Fix Python RePL Tool (#4137)

Filter out kwargs from inferred schema when determining if a tool is
single input.

Add a couple unit tests.

Move tool unit tests to the tools dir

langchain/tools/base.py

@@ -146,7 +146,8 @@ class BaseTool(ABC, BaseModel, metaclass=ToolMetaclass):
     @property
     def is_single_input(self) -> bool:
         """Whether the tool only accepts a single input."""
-        return len(self.args) == 1
+        keys = {k for k in self.args if k != "kwargs"}
+        return len(keys) == 1
 
     @property
     def args(self) -> dict:

langchain/tools/python/tool.py

@@ -36,7 +36,6 @@ class PythonREPLTool(BaseTool):
         self,
         query: str,
         run_manager: Optional[CallbackManagerForToolRun] = None,
-        **kwargs: Any,
     ) -> Any:
         """Use the tool."""
         if self.sanitize_input:
@@ -47,7 +46,6 @@ class PythonREPLTool(BaseTool):
         self,
         query: str,
         run_manager: Optional[AsyncCallbackManagerForToolRun] = None,
-        **kwargs: Any,
     ) -> Any:
         """Use the tool asynchronously."""
         raise NotImplementedError("PythonReplTool does not support async")