langchain/document_loaders/pyspark_dataframe.py/PySparkDataFrameLoader/lazy_load
class PySparkDataFrameLoader:    def lazy_load(self) -> Iterator[Document]:
        """A lazy loader for document content."""
        for row in self.rdd_df.toLocalIterator():
            metadata = {self.column_names[i]: row[i] for i in range(len(row))}
            text = metadata[self.page_content_column]
            metadata.pop(self.page_content_column)
            yield Document(page_content=text, metadata=metadata)