What is the reason behind the error: INFO:openai:error_code=None error_message='You exceeded your current quota, please check your plan and billing details.' error_param=None error_type=insufficient_quota message='OpenAI API error received' stream_error=False?

Hello,

When I try to run GPTSimpleVectorIndex.from_documents(documents), it returns AttributeError: 'dict' object has no attribute 'split', any idea on the reasons?