fix: Refactor PythonREPLToolComponent, update template, and add suppo…

…rt for None value on secretStrInput (langflow-ai#3741)

* refactor: Refactor PythonREPLToolComponent to use pydantic and langchain_utilities

* update template

* add suport for None value on secretStrInput

src/backend/base/langflow/inputs/inputs.py

@@ -273,6 +273,8 @@ def validate_value(cls, v: Any, _info):
                 )
         elif isinstance(v, (AsyncIterator, Iterator)):
             value = v
+        elif v is None:
+            value = None
         else:
             raise ValueError(f"Invalid value type `{type(v)}` for input `{_info.data['name']}`")
         return value