fix: Resolve MyPy 'Name already defined' error using TYPE_CHECKING imports

- Use TYPE_CHECKING conditional imports to avoid MyPy duplicate name definitions
- Maintains runtime conditional import behavior for WASM compatibility
- Local MyPy check now passes successfully on all 415 source files

Co-Authored-By: AJ Steers <[email protected]>

Author: devin-ai-integration[bot]

airbyte_cdk/models/airbyte_protocol_serializers.py

@@ -1,6 +1,15 @@
 # Copyright (c) 2024 Airbyte, Inc., all rights reserved.
 import sys
-from typing import Any, Dict
+from typing import TYPE_CHECKING, Any, Dict
+
+if TYPE_CHECKING:
+    from serpyco_rs import CustomType, Serializer
+else:
+    USE_RUST_BACKEND = sys.platform != "emscripten"
+    if USE_RUST_BACKEND:
+        from serpyco_rs import CustomType, Serializer
+    else:
+        from serpyco import CustomType, Serializer
 
 from .airbyte_protocol import (  # type: ignore[attr-defined] # all classes are imported to airbyte_protocol via *
     AirbyteCatalog,
@@ -14,13 +23,6 @@
     ConnectorSpecification,
 )
 
-USE_RUST_BACKEND = sys.platform != "emscripten"
-"""When run in WASM, use the pure Python backend for serpyco."""
-
-if USE_RUST_BACKEND:
-    from serpyco_rs import CustomType, Serializer
-else:
-    from serpyco import CustomType, Serializer
 
 
 class AirbyteStateBlobType(CustomType[AirbyteStateBlob, Dict[str, Any]]):