def METHOD_NAME(from_nuclides,
                     fuel,
                     flux,
                     micro_xs,
                     chain_file,
                     normalization_mode):
    if from_nuclides:
        nuclides = {}
        for nuc, dens in fuel.get_nuclide_atom_densities().items():
            nuclides[nuc] = dens
        op = IndependentOperator.from_nuclides(fuel.volume,
                                               nuclides,
                                               flux,
                                               micro_xs,
                                               chain_file,
                                               normalization_mode=normalization_mode)
    else:
        op = IndependentOperator(openmc.Materials([fuel]),
                                 [flux],
                                 [micro_xs],
                                 chain_file,
                                 normalization_mode=normalization_mode)
    return op