langchain/document_loaders/tomarkdown.py/ToMarkdownLoader/lazy_load
class ToMarkdownLoader:    def lazy_load(
        self,
    ) -> Iterator[Document]:
        """Lazily load the file."""
        response = requests.post(
            "https://2markdown.com/api/2md",
            headers={"X-Api-Key": self.api_key},
            json={"url": self.url},
        )
        text = response.json()["article"]
        metadata = {"source": self.url}
        yield Document(page_content=text, metadata=metadata)