langchain/utilities/powerbi.py/PowerBIDataset/_aget_schema
class PowerBIDataset:    async def _aget_schema(self, table: str) -> None:
        """Get the schema for a table."""
        try:
            result = await self.arun(
                f"EVALUATE TOPN({self.sample_rows_in_table_info}, {table})"
            )
            self.schemas[table] = json_to_md(result["results"][0]["tables"][0]["rows"])
        except ServerTimeoutError:
            _LOGGER.warning("Timeout while getting table info for %s", table)
            self.schemas[table] = "unknown"
        except Exception as exc:  # pylint: disable=broad-exception-caught
            _LOGGER.warning("Error while getting table info for %s: %s", table, exc)
            self.schemas[table] = "unknown"