Merge pull request #415 from byllyfish/cleanup

Update dev. dependencies. Fix pyright and ruff lint warnings.
byllyfish · Jan 28, 2024 · 4c4ab01 · 4c4ab01
2 parents 43287ee + bca24ef
commit 4c4ab01
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diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -6,7 +6,10 @@ name: ci
 on:
   push:
     branches: [ "*" ]
-
+  schedule:
+    # Every day at 2:34.
+    - cron: '34 2 * * *'
+
 permissions:
   contents: read
 

diff --git a/ci/requirements-demonet.txt b/ci/requirements-demonet.txt
@@ -1,3 +1,3 @@
-# Poetry (version 1.7.1) export at Fri Jan 19 19:48:28 MST 2024
+# Poetry (version 1.7.1) export at Sat Jan 27 14:27:45 MST 2024
 pygraphviz==1.12 ; python_version >= "3.10" and python_version < "4.0" \
     --hash=sha256:8b0b9207954012f3b670e53b8f8f448a28d12bdbbcf69249313bd8dbe680152f
diff --git a/ci/requirements-dev.txt b/ci/requirements-dev.txt
@@ -1,4 +1,4 @@
-# Poetry (version 1.7.1) export at Fri Jan 19 19:48:28 MST 2024
+# Poetry (version 1.7.1) export at Sat Jan 27 14:27:45 MST 2024
 astroid==3.0.2 ; python_version >= "3.10" and python_version < "4.0" \
     --hash=sha256:4a61cf0a59097c7bb52689b0fd63717cd2a8a14dc9f1eee97b82d814881c8c91 \
     --hash=sha256:d6e62862355f60e716164082d6b4b041d38e2a8cf1c7cd953ded5108bac8ff5c
@@ -31,59 +31,59 @@ click==8.1.7 ; python_version >= "3.10" and python_version < "4.0" \
 colorama==0.4.6 ; python_version >= "3.10" and python_version < "4.0" and (sys_platform == "win32" or platform_system == "Windows") \
     --hash=sha256:08695f5cb7ed6e0531a20572697297273c47b8cae5a63ffc6d6ed5c201be6e44 \
     --hash=sha256:4f1d9991f5acc0ca119f9d443620b77f9d6b33703e51011c16baf57afb285fc6
-coverage[toml]==7.4.0 ; python_version >= "3.10" and python_version < "4.0" \
-    --hash=sha256:04387a4a6ecb330c1878907ce0dc04078ea72a869263e53c72a1ba5bbdf380ca \
-    --hash=sha256:0676cd0ba581e514b7f726495ea75aba3eb20899d824636c6f59b0ed2f88c471 \
-    --hash=sha256:0e8d06778e8fbffccfe96331a3946237f87b1e1d359d7fbe8b06b96c95a5407a \
-    --hash=sha256:0eb3c2f32dabe3a4aaf6441dde94f35687224dfd7eb2a7f47f3fd9428e421058 \
-    --hash=sha256:109f5985182b6b81fe33323ab4707011875198c41964f014579cf82cebf2bb85 \
-    --hash=sha256:13eaf476ec3e883fe3e5fe3707caeb88268a06284484a3daf8250259ef1ba143 \
-    --hash=sha256:164fdcc3246c69a6526a59b744b62e303039a81e42cfbbdc171c91a8cc2f9446 \
-    --hash=sha256:26776ff6c711d9d835557ee453082025d871e30b3fd6c27fcef14733f67f0590 \
-    --hash=sha256:26f66da8695719ccf90e794ed567a1549bb2644a706b41e9f6eae6816b398c4a \
-    --hash=sha256:29f3abe810930311c0b5d1a7140f6395369c3db1be68345638c33eec07535105 \
-    --hash=sha256:316543f71025a6565677d84bc4df2114e9b6a615aa39fb165d697dba06a54af9 \
-    --hash=sha256:36b0ea8ab20d6a7564e89cb6135920bc9188fb5f1f7152e94e8300b7b189441a \
-    --hash=sha256:3cc9d4bc55de8003663ec94c2f215d12d42ceea128da8f0f4036235a119c88ac \
-    --hash=sha256:485e9f897cf4856a65a57c7f6ea3dc0d4e6c076c87311d4bc003f82cfe199d25 \
-    --hash=sha256:5040148f4ec43644702e7b16ca864c5314ccb8ee0751ef617d49aa0e2d6bf4f2 \
-    --hash=sha256:51456e6fa099a8d9d91497202d9563a320513fcf59f33991b0661a4a6f2ad450 \
-    --hash=sha256:53d7d9158ee03956e0eadac38dfa1ec8068431ef8058fe6447043db1fb40d932 \
-    --hash=sha256:5a10a4920def78bbfff4eff8a05c51be03e42f1c3735be42d851f199144897ba \
-    --hash=sha256:5b14b4f8760006bfdb6e08667af7bc2d8d9bfdb648351915315ea17645347137 \
-    --hash=sha256:5b2ccb7548a0b65974860a78c9ffe1173cfb5877460e5a229238d985565574ae \
-    --hash=sha256:697d1317e5290a313ef0d369650cfee1a114abb6021fa239ca12b4849ebbd614 \
-    --hash=sha256:6ae8c9d301207e6856865867d762a4b6fd379c714fcc0607a84b92ee63feff70 \
-    --hash=sha256:707c0f58cb1712b8809ece32b68996ee1e609f71bd14615bd8f87a1293cb610e \
-    --hash=sha256:74775198b702868ec2d058cb92720a3c5a9177296f75bd97317c787daf711505 \
-    --hash=sha256:756ded44f47f330666843b5781be126ab57bb57c22adbb07d83f6b519783b870 \
-    --hash=sha256:76f03940f9973bfaee8cfba70ac991825611b9aac047e5c80d499a44079ec0bc \
-    --hash=sha256:79287fd95585ed36e83182794a57a46aeae0b64ca53929d1176db56aacc83451 \
-    --hash=sha256:799c8f873794a08cdf216aa5d0531c6a3747793b70c53f70e98259720a6fe2d7 \
-    --hash=sha256:7d360587e64d006402b7116623cebf9d48893329ef035278969fa3bbf75b697e \
-    --hash=sha256:80b5ee39b7f0131ebec7968baa9b2309eddb35b8403d1869e08f024efd883566 \
-    --hash=sha256:815ac2d0f3398a14286dc2cea223a6f338109f9ecf39a71160cd1628786bc6f5 \
-    --hash=sha256:83c2dda2666fe32332f8e87481eed056c8b4d163fe18ecc690b02802d36a4d26 \
-    --hash=sha256:846f52f46e212affb5bcf131c952fb4075b55aae6b61adc9856222df89cbe3e2 \
-    --hash=sha256:936d38794044b26c99d3dd004d8af0035ac535b92090f7f2bb5aa9c8e2f5cd42 \
-    --hash=sha256:9864463c1c2f9cb3b5db2cf1ff475eed2f0b4285c2aaf4d357b69959941aa555 \
-    --hash=sha256:995ea5c48c4ebfd898eacb098164b3cc826ba273b3049e4a889658548e321b43 \
-    --hash=sha256:a1526d265743fb49363974b7aa8d5899ff64ee07df47dd8d3e37dcc0818f09ed \
-    --hash=sha256:a56de34db7b7ff77056a37aedded01b2b98b508227d2d0979d373a9b5d353daa \
-    --hash=sha256:a7c97726520f784239f6c62506bc70e48d01ae71e9da128259d61ca5e9788516 \
-    --hash=sha256:b8e99f06160602bc64da35158bb76c73522a4010f0649be44a4e167ff8555952 \
-    --hash=sha256:bb1de682da0b824411e00a0d4da5a784ec6496b6850fdf8c865c1d68c0e318dd \
-    --hash=sha256:bf477c355274a72435ceb140dc42de0dc1e1e0bf6e97195be30487d8eaaf1a09 \
-    --hash=sha256:bf635a52fc1ea401baf88843ae8708591aa4adff875e5c23220de43b1ccf575c \
-    --hash=sha256:bfd5db349d15c08311702611f3dccbef4b4e2ec148fcc636cf8739519b4a5c0f \
-    --hash=sha256:c530833afc4707fe48524a44844493f36d8727f04dcce91fb978c414a8556cc6 \
-    --hash=sha256:cc6d65b21c219ec2072c1293c505cf36e4e913a3f936d80028993dd73c7906b1 \
-    --hash=sha256:cd3c1e4cb2ff0083758f09be0f77402e1bdf704adb7f89108007300a6da587d0 \
-    --hash=sha256:cfd2a8b6b0d8e66e944d47cdec2f47c48fef2ba2f2dff5a9a75757f64172857e \
-    --hash=sha256:d0ca5c71a5a1765a0f8f88022c52b6b8be740e512980362f7fdbb03725a0d6b9 \
-    --hash=sha256:e7defbb9737274023e2d7af02cac77043c86ce88a907c58f42b580a97d5bcca9 \
-    --hash=sha256:e9d1bf53c4c8de58d22e0e956a79a5b37f754ed1ffdbf1a260d9dcfa2d8a325e \
-    --hash=sha256:ea81d8f9691bb53f4fb4db603203029643caffc82bf998ab5b59ca05560f4c06
+coverage[toml]==7.4.1 ; python_version >= "3.10" and python_version < "4.0" \
+    --hash=sha256:0193657651f5399d433c92f8ae264aff31fc1d066deee4b831549526433f3f61 \
+    --hash=sha256:02f2edb575d62172aa28fe00efe821ae31f25dc3d589055b3fb64d51e52e4ab1 \
+    --hash=sha256:0491275c3b9971cdbd28a4595c2cb5838f08036bca31765bad5e17edf900b2c7 \
+    --hash=sha256:077d366e724f24fc02dbfe9d946534357fda71af9764ff99d73c3c596001bbd7 \
+    --hash=sha256:10e88e7f41e6197ea0429ae18f21ff521d4f4490aa33048f6c6f94c6045a6a75 \
+    --hash=sha256:18e961aa13b6d47f758cc5879383d27b5b3f3dcd9ce8cdbfdc2571fe86feb4dd \
+    --hash=sha256:1a78b656a4d12b0490ca72651fe4d9f5e07e3c6461063a9b6265ee45eb2bdd35 \
+    --hash=sha256:1ed4b95480952b1a26d863e546fa5094564aa0065e1e5f0d4d0041f293251d04 \
+    --hash=sha256:23b27b8a698e749b61809fb637eb98ebf0e505710ec46a8aa6f1be7dc0dc43a6 \
+    --hash=sha256:23f5881362dcb0e1a92b84b3c2809bdc90db892332daab81ad8f642d8ed55042 \
+    --hash=sha256:32a8d985462e37cfdab611a6f95b09d7c091d07668fdc26e47a725ee575fe166 \
+    --hash=sha256:3468cc8720402af37b6c6e7e2a9cdb9f6c16c728638a2ebc768ba1ef6f26c3a1 \
+    --hash=sha256:379d4c7abad5afbe9d88cc31ea8ca262296480a86af945b08214eb1a556a3e4d \
+    --hash=sha256:3cacfaefe6089d477264001f90f55b7881ba615953414999c46cc9713ff93c8c \
+    --hash=sha256:3e3424c554391dc9ef4a92ad28665756566a28fecf47308f91841f6c49288e66 \
+    --hash=sha256:46342fed0fff72efcda77040b14728049200cbba1279e0bf1188f1f2078c1d70 \
+    --hash=sha256:536d609c6963c50055bab766d9951b6c394759190d03311f3e9fcf194ca909e1 \
+    --hash=sha256:5d6850e6e36e332d5511a48a251790ddc545e16e8beaf046c03985c69ccb2676 \
+    --hash=sha256:6008adeca04a445ea6ef31b2cbaf1d01d02986047606f7da266629afee982630 \
+    --hash=sha256:64e723ca82a84053dd7bfcc986bdb34af8d9da83c521c19d6b472bc6880e191a \
+    --hash=sha256:6b00e21f86598b6330f0019b40fb397e705135040dbedc2ca9a93c7441178e74 \
+    --hash=sha256:6d224f0c4c9c98290a6990259073f496fcec1b5cc613eecbd22786d398ded3ad \
+    --hash=sha256:6dceb61d40cbfcf45f51e59933c784a50846dc03211054bd76b421a713dcdf19 \
+    --hash=sha256:7ac8f8eb153724f84885a1374999b7e45734bf93a87d8df1e7ce2146860edef6 \
+    --hash=sha256:85ccc5fa54c2ed64bd91ed3b4a627b9cce04646a659512a051fa82a92c04a448 \
+    --hash=sha256:869b5046d41abfea3e381dd143407b0d29b8282a904a19cb908fa24d090cc018 \
+    --hash=sha256:8bdb0285a0202888d19ec6b6d23d5990410decb932b709f2b0dfe216d031d218 \
+    --hash=sha256:8dfc5e195bbef80aabd81596ef52a1277ee7143fe419efc3c4d8ba2754671756 \
+    --hash=sha256:8e738a492b6221f8dcf281b67129510835461132b03024830ac0e554311a5c54 \
+    --hash=sha256:918440dea04521f499721c039863ef95433314b1db00ff826a02580c1f503e45 \
+    --hash=sha256:9641e21670c68c7e57d2053ddf6c443e4f0a6e18e547e86af3fad0795414a628 \
+    --hash=sha256:9d2f9d4cc2a53b38cabc2d6d80f7f9b7e3da26b2f53d48f05876fef7956b6968 \
+    --hash=sha256:a07f61fc452c43cd5328b392e52555f7d1952400a1ad09086c4a8addccbd138d \
+    --hash=sha256:a3277f5fa7483c927fe3a7b017b39351610265308f5267ac6d4c2b64cc1d8d25 \
+    --hash=sha256:a4a3907011d39dbc3e37bdc5df0a8c93853c369039b59efa33a7b6669de04c60 \
+    --hash=sha256:aeb2c2688ed93b027eb0d26aa188ada34acb22dceea256d76390eea135083950 \
+    --hash=sha256:b094116f0b6155e36a304ff912f89bbb5067157aff5f94060ff20bbabdc8da06 \
+    --hash=sha256:b8ffb498a83d7e0305968289441914154fb0ef5d8b3157df02a90c6695978295 \
+    --hash=sha256:b9bb62fac84d5f2ff523304e59e5c439955fb3b7f44e3d7b2085184db74d733b \
+    --hash=sha256:c61f66d93d712f6e03369b6a7769233bfda880b12f417eefdd4f16d1deb2fc4c \
+    --hash=sha256:ca6e61dc52f601d1d224526360cdeab0d0712ec104a2ce6cc5ccef6ed9a233bc \
+    --hash=sha256:ca7b26a5e456a843b9b6683eada193fc1f65c761b3a473941efe5a291f604c74 \
+    --hash=sha256:d12c923757de24e4e2110cf8832d83a886a4cf215c6e61ed506006872b43a6d1 \
+    --hash=sha256:d17bbc946f52ca67adf72a5ee783cd7cd3477f8f8796f59b4974a9b59cacc9ee \
+    --hash=sha256:dfd1e1b9f0898817babf840b77ce9fe655ecbe8b1b327983df485b30df8cc011 \
+    --hash=sha256:e0860a348bf7004c812c8368d1fc7f77fe8e4c095d661a579196a9533778e156 \
+    --hash=sha256:f2f5968608b1fe2a1d00d01ad1017ee27efd99b3437e08b83ded9b7af3f6f766 \
+    --hash=sha256:f3771b23bb3675a06f5d885c3630b1d01ea6cac9e84a01aaf5508706dba546c5 \
+    --hash=sha256:f68ef3660677e6624c8cace943e4765545f8191313a07288a53d3da188bd8581 \
+    --hash=sha256:f86f368e1c7ce897bf2457b9eb61169a44e2ef797099fb5728482b8d69f3f016 \
+    --hash=sha256:f90515974b39f4dea2f27c0959688621b46d96d5a626cf9c53dbc653a895c05c \
+    --hash=sha256:fe558371c1bdf3b8fa03e097c523fb9645b8730399c14fe7721ee9c9e2a545d3
 dill==0.3.7 ; python_version >= "3.10" and python_version < "4.0" \
     --hash=sha256:76b122c08ef4ce2eedcd4d1abd8e641114bfc6c2867f49f3c41facf65bf19f5e \
     --hash=sha256:cc1c8b182eb3013e24bd475ff2e9295af86c1a38eb1aff128dac8962a9ce3c03
@@ -267,9 +267,9 @@ pdoc==14.4.0 ; python_version >= "3.10" and python_version < "4.0" \
 platformdirs==4.1.0 ; python_version >= "3.10" and python_version < "4.0" \
     --hash=sha256:11c8f37bcca40db96d8144522d925583bdb7a31f7b0e37e3ed4318400a8e2380 \
     --hash=sha256:906d548203468492d432bcb294d4bc2fff751bf84971fbb2c10918cc206ee420
-pluggy==1.3.0 ; python_version >= "3.10" and python_version < "4.0" \
-    --hash=sha256:cf61ae8f126ac6f7c451172cf30e3e43d3ca77615509771b3a984a0730651e12 \
-    --hash=sha256:d89c696a773f8bd377d18e5ecda92b7a3793cbe66c87060a6fb58c7b6e1061f7
+pluggy==1.4.0 ; python_version >= "3.10" and python_version < "4.0" \
+    --hash=sha256:7db9f7b503d67d1c5b95f59773ebb58a8c1c288129a88665838012cfb07b8981 \
+    --hash=sha256:8c85c2876142a764e5b7548e7d9a0e0ddb46f5185161049a79b7e974454223be
 prometheus-client==0.19.0 ; python_version >= "3.10" and python_version < "4.0" \
     --hash=sha256:4585b0d1223148c27a225b10dbec5ae9bc4c81a99a3fa80774fa6209935324e1 \
     --hash=sha256:c88b1e6ecf6b41cd8fb5731c7ae919bf66df6ec6fafa555cd6c0e16ca169ae92
@@ -294,9 +294,9 @@ pygments==2.17.2 ; python_version >= "3.10" and python_version < "4.0" \
 pylint==3.0.3 ; python_version >= "3.10" and python_version < "4.0" \
     --hash=sha256:58c2398b0301e049609a8429789ec6edf3aabe9b6c5fec916acd18639c16de8b \
     --hash=sha256:7a1585285aefc5165db81083c3e06363a27448f6b467b3b0f30dbd0ac1f73810
-pyright==1.1.347 ; python_version >= "3.10" and python_version < "4.0" \
-    --hash=sha256:14dd31b594aa3ec464894f66b8a2d206ebef1501e52789eb88cf2a79b0907fbe \
-    --hash=sha256:17ea09322f60080f82abc4e622e43d1a5ebaa407ba86963b15b2bc01cca256e0
+pyright==1.1.348 ; python_version >= "3.10" and python_version < "4.0" \
+    --hash=sha256:1c6994546f7ab130b9da8c357f8b2a99bef268b6d8ae2eae292bde66923aa7af \
+    --hash=sha256:e7d4df504c4c082b5c3725a8c15fc3fda62da5d09fc77994baa77f359a1b62f2
 pytest-asyncio==0.21.1 ; python_version >= "3.10" and python_version < "4.0" \
     --hash=sha256:40a7eae6dded22c7b604986855ea48400ab15b069ae38116e8c01238e9eeb64d \
     --hash=sha256:8666c1c8ac02631d7c51ba282e0c69a8a452b211ffedf2599099845da5c5c37b

diff --git a/ci/requirements.txt b/ci/requirements.txt
@@ -1,4 +1,4 @@
-# Poetry (version 1.7.1) export at Fri Jan 19 19:48:28 MST 2024
+# Poetry (version 1.7.1) export at Sat Jan 27 14:27:45 MST 2024
 grpcio==1.60.0 ; python_version >= "3.10" and python_version < "4.0" \
     --hash=sha256:073f959c6f570797272f4ee9464a9997eaf1e98c27cb680225b82b53390d61e6 \
     --hash=sha256:0fd3b3968ffe7643144580f260f04d39d869fcc2cddb745deef078b09fd2b328 \

diff --git a/examples/gnmi/demo3.py b/examples/gnmi/demo3.py
@@ -26,12 +26,14 @@ async def main():
             print(f"initial: {update.path['name']} is {update.value}")
 
         # Run a background task to toggle the interface status.
-        _task = asyncio.create_task(toggle_enabled(names))
+        task = asyncio.create_task(toggle_enabled(names))
 
-        # Listen for status updates.
+        # Listen for status updates (infinite loop).
         async for update in sub.updates():
             print(f"update:  {update.path['name']} is {update.value}")
 
+        task.cancel()
+
 
 async def toggle_enabled(names: list[str]):
     "Repeatedly disable and enable interfaces using a separate GNMI client."

diff --git a/finsy/p4entity.py b/finsy/p4entity.py
@@ -202,19 +202,19 @@ class _P4Writable(P4Entity):
 
     def __pos__(self) -> Self:
         if self._update_type != P4UpdateType.UNSPECIFIED:
-            raise ValueError(f"update type already specified")
+            raise ValueError("update type already specified")
         self._update_type = P4UpdateType.INSERT
         return self
 
     def __neg__(self) -> Self:
         if self._update_type != P4UpdateType.UNSPECIFIED:
-            raise ValueError(f"update type already specified")
+            raise ValueError("update type already specified")
         self._update_type = P4UpdateType.DELETE
         return self
 
     def __invert__(self) -> Self:
         if self._update_type != P4UpdateType.UNSPECIFIED:
-            raise ValueError(f"update type already specified")
+            raise ValueError("update type already specified")
         self._update_type = P4UpdateType.MODIFY
         return self
 

diff --git a/finsy/p4schema.py b/finsy/p4schema.py
@@ -221,7 +221,7 @@ class _P4AnnoMixin:
     _annotations: list["P4Annotation"]
 
     def __init__(self, pbuf: Any):
-        super().__init__(pbuf)  # pyright: ignore[reportGeneralTypeIssues]
+        super().__init__(pbuf)  # pyright: ignore[reportCallIssue]
         self._annotations = _parse_annotations(pbuf)
 
     @property
@@ -2127,14 +2127,14 @@ def __init__(self):
     def get(self, key: tuple[str, str] | tuple[int, int]) -> P4ExternInstance | None:
         "Retrieve item by name. Return None if not found."
         if isinstance(key[0], int):
-            return self._by_id.get(key)  # pyright: ignore[reportGeneralTypeIssues]
-        return self._by_name.get(key)  # pyright: ignore[reportGeneralTypeIssues]
+            return self._by_id.get(key)  # pyright: ignore[reportArgumentType]
+        return self._by_name.get(key)  # pyright: ignore[reportArgumentType]
 
     def __getitem__(self, key: tuple[str, str] | tuple[int, int]) -> P4ExternInstance:
         value = self.get(key)
         if value is None:
             self._key_error(key)
-        return value  # pyright: ignore[reportGeneralTypeIssues]
+        return value  # pyright: ignore[reportReturnType]
 
     def __iter__(self) -> Iterator[P4ExternInstance]:
         return iter(self._by_name.values())

diff --git a/finsy/runner.py b/finsy/runner.py
@@ -29,19 +29,19 @@ def _sigterm_cancel_task(task: asyncio.Task[Any]) -> None:
 
 async def _finsy_boilerplate(coro: Coroutine[Any, Any, None]):
     "Wrap main async function and implement boilerplate."
-
-    # Activate logging.
     logging.basicConfig(
         level=logging.INFO,
         format="%(created).03f %(levelname)s %(name)s %(message)s",
     )
 
     if sys.platform != "win32":
         # Boilerplate to shutdown cleanly upon SIGTERM signal.
+        current_task = asyncio.current_task()
+        assert current_task is not None
         asyncio.get_running_loop().add_signal_handler(
             signal.SIGTERM,
             _sigterm_cancel_task,
-            asyncio.current_task(),
+            current_task,
         )
 
     # Enable caching of P4Info definitions.

diff --git a/finsy/test/demonet.py b/finsy/test/demonet.py
@@ -14,16 +14,37 @@
 from ipaddress import IPv4Network, IPv6Network
 from pathlib import Path
 from types import TracebackType
-from typing import Any, ClassVar, Sequence
+from typing import Any, ClassVar, Protocol, Sequence
 
 from shellous import Command, Prompt, sh
 
 from finsy import MACAddress
 
-try:
-    import pygraphviz as pgv  # type: ignore
-except ImportError:
-    pgv = None
+
+class GraphAPI(Protocol):
+    """Protocol implemented by pygraphviz Graph.
+
+    pygraphviz is an optional dependency; this Protocol facilitates typing.
+    """
+
+    def __init__(self, **attr: Any):
+        ...
+
+    def add_node(self, n: Any, **attr: Any) -> None:
+        ...
+
+    def add_edge(self, u: Any, v: Any, **attr: Any) -> None:
+        ...
+
+    def layout(self) -> None:
+        ...
+
+    def draw(self, path: str | None) -> bytes | None:
+        ...
+
+    def to_string(self) -> str:
+        ...
+
 
 # pyright: reportUnknownMemberType=false
 
@@ -237,20 +258,20 @@ def _json_default(obj: object):
             return str(obj)
 
         try:
-            return asdict(obj)  # pyright: ignore[reportGeneralTypeIssues]
+            return asdict(obj)  # pyright: ignore[reportArgumentType]
         except TypeError as ex:
             raise ValueError(
                 f"DemoNet can't serialize {type(obj).__name__!r}: {obj!r}"
             ) from ex
 
-    def to_graph(self) -> "pgv.AGraph":
+    def to_graph(self) -> GraphAPI:
         "Create a pygraphviz Graph of the network."
-        if pgv is None:
-            raise RuntimeError("ERROR: pygraphviz is not installed.")
+        try:
+            import pygraphviz as pgv  # type: ignore
+        except ImportError:
+            raise RuntimeError("ERROR: pygraphviz is not installed.") from None
 
-        graph = pgv.AGraph(
-            **_PyGraphStyle.graph,  # pyright: ignore[reportGeneralTypeIssues]
-        )
+        graph = pgv.AGraph(**_PyGraphStyle.graph)
 
         for item in self.items:
             match item:
@@ -611,7 +632,7 @@ def _get_local_ipv4_address():
 class _PyGraphStyle:
     "Style defaults for different graphviz elements."
 
-    graph: ClassVar[dict[str, str]] = dict(
+    graph: ClassVar[dict[str, Any]] = dict(
         bgcolor="lightblue",
         margin="0",
         pad="0.25",