@overrides<EOL><INDENT>def get_doc_content(self, doc_id: Any) -> Optional[str]:<DEDENT>
cursor = self.connect.cursor()<EOL>cursor.execute(<EOL>"<STR_LIT>".format(self.db_name),<EOL>(doc_id,)<EOL>)<EOL>result = cursor.fetchone()<EOL>cursor.close()<EOL>return result if result is None else result[<NUM_LIT:0>]<EOL>
Get document content by id.

        Args:
            doc_id: a document id

        Returns:
            document content if success, else raise Exception