langchain/document_loaders/facebook_chat.py/FacebookChatLoader/load
class FacebookChatLoader:    def load(self) -> List[Document]:
        """Load documents."""
        p = Path(self.file_path)

        with open(p, encoding="utf8") as f:
            d = json.load(f)

        text = "".join(
            concatenate_rows(message)
            for message in d["messages"]
            if message.get("content") and isinstance(message["content"], str)
        )
        metadata = {"source": str(p)}

        return [Document(page_content=text, metadata=metadata)]