Create Langchain LLM converter to quickly supply it to Langchain's chain (#102)

* Create Langchain LLM converter to quickly supply it to Langchain's chain

* Clean up

knowledgehub/llms/completions/langchain_based.py

@@ -45,6 +45,9 @@ class LCCompletionMixin:
             logits=[],
         )
 
+    def to_langchain_format(self):
+        return self._obj
+
     def __repr__(self):
         kwargs = []
         for key, value_obj in self._kwargs.items():