Error using VectorstoreIndexCreator 'builtin_function_or_method' object has no attribute '__func__'

Short Course Q&A LangChain: Chat with Your Data
1

I am trying to load a pdf and useRetrievalQA but
I was getting that docarray was not installed, but langchain was, even trying to force install langchain[docarray] did not work, I had to downgrade it.
now I get this error

AttributeError: ‘builtin_function_or_method’ object has no attribute ‘func’
that is my code:

# workaround for some bug inside langchain that tryes to initiate some openai stuff even though it is not been used
import os
os.environ['OPENAI_API_KEY'] = 'dummy_key'


from langchain_community.document_loaders import PyMuPDFLoader
from langchain.indexes import VectorstoreIndexCreator
from langchain.vectorstores import DocArrayInMemorySearch

file = "file-example_PDF_1MB.pdf"

loader = PyMuPDFLoader(file)
documents = loader.load()

#this fails
index = VectorstoreIndexCreator(
    vectorstore_cls=DocArrayInMemorySearch
).from_loaders([loader])

Anyone having this too? Looks like langchain is broken