Removing LangChain and Rebuilding Executor (#1322)

* rebuilding executor

* removing langchain

* Making all tests good

* fixing types and adding ability for nor using system prompts

* improving types

* pleasing the types gods

* pleasing the types gods

* fixing parser, tools and executor

* making sure all tests pass

* final pass

* fixing type

* Updating Docs

* preparing to cut new version

src/crewai/tasks/task_output.py

@@ -35,7 +35,7 @@ class TaskOutput(BaseModel):
         return self
 
     @property
-    def json(self) -> Optional[str]:
+    def json(self) -> str:
         if self.output_format != OutputFormat.JSON:
             raise ValueError(
                 """