def rowgroupmap(table, key, mapper, header=None, presorted=False,
                buffersize=None, tempdir=None, cache=True):

    return RowGroupMapView(table, key, mapper, header=header,
                           presorted=presorted,
                           buffersize=buffersize, tempdir=tempdir, cache=cache)
Returns number of rows in table.
dataset/ETHPy150Open alimanfoo/petl/petl/transform/maps.py/rowgroupmap--crossover with--dataset/ETHPy150Open google/textfsm/texttable.py/TextTable._GetSize