Fix typehinting of functions

gpt_json/gpt.py

@@ -89,7 +89,7 @@ class RunResponse(Generic[SchemaType], BaseModel):
     raw_response: GPTMessage | None
     response: SchemaType | None
     fix_transforms: FixTransforms | None
-    function_call: Callable[..., BaseModel] | None
+    function_call: Callable[[BaseModel], Any] | None
     function_arg: BaseModel | None
 
 
@@ -108,7 +108,7 @@ def __init__(
         model: GPTModelVersion | str = GPTModelVersion.GPT_4,
         auto_trim: bool = False,
         auto_trim_response_overhead: int = 0,
-        functions: list[Callable[..., BaseModel]] | None = None,
+        functions: list[Callable[[Any], Any]] | None = None,
         # For messages that are relatively deterministic
         temperature=0.2,
         timeout: int | None = None,
@@ -134,7 +134,13 @@ def __init__(
         self.openai_max_retries = openai_max_retries
         self.openai_arguments = kwargs
         self.schema_model = self._cls_schema_model
-        self.functions = {function_to_name(fn): fn for fn in (functions or [])}
+        self.functions = {
+            function_to_name(cast_fn): cast_fn
+            for fn in (functions or [])
+            # Use an explicit cast; Callable can't be typehinted with BaseModel directly
+            # because [BaseModel] is considered invariant with subclasses
+            for cast_fn in [cast(Callable[[BaseModel], Any], fn)]
+        }
         self.__class__._cls_schema_model = None
 
         if not self.schema_model:
@@ -233,7 +239,7 @@ async def run(
                 function_arg=None,
             )
 
-        function_call: Callable[..., BaseModel] | None = None
+        function_call: Callable[[BaseModel], Any] | None = None
         function_parsed: BaseModel | None = None
 
         if response_message.get("function_call"):