langchain/document_loaders/parsers/generic.py/MimeTypeBasedParser/lazy_parse
class MimeTypeBasedParser:    def lazy_parse(self, blob: Blob) -> Iterator[Document]:
        """Load documents from a blob."""
        mimetype = blob.mimetype

        if mimetype is None:
            raise ValueError(f"{blob} does not have a mimetype.")

        if mimetype in self.handlers:
            handler = self.handlers[mimetype]
            yield from handler.lazy_parse(blob)
        else:
            if self.fallback_parser is not None:
                yield from self.fallback_parser.lazy_parse(blob)
            else:
                raise ValueError(f"Unsupported mime type: {mimetype}")