fix(types): resolve MyPy assignment type errors in logging_utils and vertex transformation

logging_utils.py: annotate `copy` as `Union[dict, list]` so the list-branch
reassignment is compatible with the dict-branch assignment in the same scope.

transformation.py: pre-declare `project_id: Optional[str]` before the
if/else block so both branches (str from _ensure_access_token, Optional[str]
from vertex_ai_project) are compatible; use `project_id or ""` when passing
to get_complete_vertex_url which requires str.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

litellm/litellm_core_utils/logging_utils.py

@@ -101,7 +101,7 @@ def _truncate_base64_in_value(value: Any) -> Any:
                 if isinstance(v, str):
                     container[k] = _truncate_base64_in_string(v)
                 elif isinstance(v, dict):
-                    copy = {ck: cv for ck, cv in v.items()}
+                    copy: Union[dict, list] = {ck: cv for ck, cv in v.items()}
                     container[k] = copy
                     stack.append((copy, depth + 1))
                 elif isinstance(v, list):

litellm/llms/vertex_ai/vertex_ai_partner_models/anthropic/experimental_pass_through/transformation.py

@@ -34,6 +34,7 @@ class VertexAIPartnerModelsAnthropicMessagesConfig(AnthropicMessagesConfig, Vert
         vertex_ai_project = VertexBase.safe_get_vertex_ai_project(litellm_params)
         vertex_ai_location = VertexBase.safe_get_vertex_ai_location(litellm_params)
         
+        project_id: Optional[str] = None
         if "Authorization" not in headers:
             vertex_credentials = VertexBase.safe_get_vertex_ai_credentials(litellm_params)
 
@@ -54,7 +55,7 @@ class VertexAIPartnerModelsAnthropicMessagesConfig(AnthropicMessagesConfig, Vert
                 custom_api_base=api_base,
                 vertex_location=vertex_ai_location,
                 vertex_project=vertex_ai_project,
-                project_id=project_id,
+                project_id=project_id or "",
                 partner=VertexPartnerProvider.claude,
                 stream=optional_params.get("stream", False),
                 model=model,