Async call of OpenAISimilarityScorer is slower than sync version

Fixes #160

src/langcheck/metrics/eval_clients/_openai.py

@@ -409,26 +409,25 @@ def __init__(
         self.openai_args = openai_args
         self._use_async = use_async
 
+    async def _async_embed(self, inputs: list[str]) -> torch.Tensor:
+      if self.openai_args:
+          responses = await self.openai_client.embeddings.create(
+              input=inputs, **self.openai_args
+          )
+      else:
+          responses = await self.openai_client.embeddings.create(
+              input=inputs, model="text-embedding-3-small"
+          )
+      return responses
+
     def _embed(self, inputs: list[str]) -> torch.Tensor:
         """Embed the inputs using the OpenAI API."""
 
         # TODO: Fix that this async call could be much slower than the sync
         # version. https://github.com/citadel-ai/langcheck/issues/160
         if self._use_async:
-
-            async def _call_async_api() -> Any:
-                assert isinstance(self.openai_client, AsyncOpenAI)
-                if self.openai_args:
-                    responses = await self.openai_client.embeddings.create(
-                        input=inputs, **self.openai_args
-                    )
-                else:
-                    responses = await self.openai_client.embeddings.create(
-                        input=inputs, model="text-embedding-3-small"
-                    )
-                return responses
-
-            embed_response = asyncio.run(_call_async_api())
+            assert isinstance(self.openai_client, AsyncOpenAI)
+            embed_response = asyncio.get_event_loop().run_until_complete(self._async_embed(inputs))
             embeddings = [item.embedding for item in embed_response.data]
 
         else: