docstrings experimental (#7969)

- added/changed docstring for `experimental`
- added/changed docstrings for different artifacts
- 
@baskaryan

libs/experimental/langchain_experimental/cpal/constants.py

@@ -2,6 +2,8 @@ from enum import Enum
 
 
 class Constant(Enum):
+    """Enum for constants used in the CPAL."""
+
     narrative_input = "narrative_input"
     chain_answer = "chain_answer"  # natural language answer
     chain_data = "chain_data"  # pydantic instance