community: add args_schema to SearxSearch (#22954)

This change adds args_schema (pydantic BaseModel) to SearxSearchRun for
correct schema formatting on LLM function calls

Issue: currently using SearxSearchRun with OpenAI function calling
returns the following error "TypeError: SearxSearchRun._run() got an
unexpected keyword argument '__arg1' ".

This happens because the schema sent to the LLM is "input:
'{"__arg1":"foobar"}'" while the method should be called with the
"query" parameter.

---------

Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>

libs/community/langchain_community/tools/searx_search/tool.py

@@ -1,16 +1,22 @@
 """Tool for the SearxNG search API."""
-from typing import Optional
+from typing import Optional, Type
 
 from langchain_core.callbacks import (
     AsyncCallbackManagerForToolRun,
     CallbackManagerForToolRun,
 )
-from langchain_core.pydantic_v1 import Extra, Field
+from langchain_core.pydantic_v1 import BaseModel, Extra, Field
 from langchain_core.tools import BaseTool
 
 from langchain_community.utilities.searx_search import SearxSearchWrapper
 
 
+class SearxSearchQueryInput(BaseModel):
+    """Input for the SearxSearch tool."""
+
+    query: str = Field(description="query to look up on searx")
+
+
 class SearxSearchRun(BaseTool):
     """Tool that queries a Searx instance."""
 
@@ -22,6 +28,7 @@ class SearxSearchRun(BaseTool):
     )
     wrapper: SearxSearchWrapper
     kwargs: dict = Field(default_factory=dict)
+    args_schema: Type[BaseModel] = SearxSearchQueryInput
 
     def _run(
         self,