def transform(tagname, attributes, contents, context, bind):
    for fn in _transforms:
        contents = fn(tagname, attributes, contents, context, bind)
    return contents
Splits the mapping into groups by key dimension which are then
dataset/ETHPy150Open jek/flatland/flatland/out/generic.py/transform--crossover with--dataset/ETHPy150Open ioam/holoviews/holoviews/core/ndmapping.py/MultiDimensionalMapping.groupby