I get this error message

<ipython-input-141-b8110c573881> in <cell line: 1>()
----> 1 final_chain.invoke({"question":"Count of Agencies?"})

25 frames
/usr/local/lib/python3.10/dist-packages/tiktoken/core.py in encode_ordinary(self, text)
     67         """
     68         try:
---> 69             return self._core_bpe.encode_ordinary(text)
     70         except UnicodeEncodeError:
     71             # See comment in encode

TypeError: argument 'text': 'dict' object cannot be converted to 'PyString'

while invoking retriever_chain.invoke(“actual question string”). The response is generated without error,but while invoking it from final_chain.invoke({“question”:”actual question”}). Getting an typeerror.
This is the code:

vectorstore = Chroma.from_documents(documents, embedding_function)
retriever = vectorstore.as_retriever()
retriever_chain = (
    {"context": retriever, "question": RunnablePassthrough()}
    | retriever_prompt
    | llm
    | StrOutputParser()
)
final_chain = (RunnablePassthrough.assign(context=retriever_chain, table_names_to_assign = table_chain) | generate_sql_query)

I tried to pass question to a retrieval chain and question is passed as a dict, but it must be a string.