PERF: GroupBy.std operate blockwise instead of column-wise (#43115)
PERF: GroupBy.std operate blockwise instead of column-wise (#43115)


jorisvandenbossche/pandas,pandas-dev/pandas,pandas-dev/pandas,jorisvandenbossche/pandas,datapythonista/pandas,rs2/pandas,dsm054/pandas,jorisvandenbossche/pandas,rs2/pandas,dsm054/pandas,dsm054/pandas,datapythonista/pandas,rs2/pandas,dsm054/pandas,rs2/pandas,datapythonista/pandas,pandas-dev/pandas,datapythonista/pandas,dsm054/pandas,jorisvandenbossche/pandas,pandas-dev/pandas