AttributeError: type object 'Pinecone' has no attribute 'from_existing_index'.

This happenes when there are two Pinecones that you installed when importing from langchain.vectorstore and also pinecone itself. so I the method so called 'from_existing_index' only exist in Pinecone from langchain. so when import from langchain ... use this:: 'from langchain.vectorstores import Pinecode as Pi' and then use Pi when you are trying to access the attribute 'from_existing_index'

I hope you understood it.