def get_mod_func(callback):
    dot = callback.rfind('.')
    if dot == -1:
        return callback, ''
    return callback[:dot], callback[dot + 1:]
return my resampler or raise if we have an invalid axis
dataset/ETHPy150Open sympy/sympy/sympy/utilities/source.py/get_mod_func--crossover with--dataset/ETHPy150Open pydata/pandas/pandas/tseries/resample.py/TimeGrouper._get_resampler