Fix method return type (strict python noticed we return None here)

scripts/py_matter_idl/matter_idl/lint/lint_rules_parser.py

@@ -5,7 +5,7 @@
 import xml.etree.ElementTree
 from dataclasses import dataclass
 from enum import Enum, auto
-from typing import List, MutableMapping, Tuple, Union
+from typing import List, MutableMapping, Optional, Tuple, Union
 
 from lark import Lark
 from lark.visitors import Discard, Transformer, v_args
@@ -167,7 +167,7 @@ def GetLinterRules(self):
     def RequireAttribute(self, r: AttributeRequirement):
         self._required_attributes_rule.RequireAttribute(r)
 
-    def FindClusterCode(self, name: str) -> Tuple[str, int]:
+    def FindClusterCode(self, name: str) -> Optionarl[Tuple[str, int]]:
         if name not in self._cluster_codes:
             # Name may be a number. If this can be parsed as a number, accept it anyway
             try: