def METHOD_NAME(self, container, truth, n_files):
    CM2_TO_M2 = 1e-4
    weighted_aeff = (
        CM2_TO_M2
        * truth["OneWeight"]
        / n_files
        / truth["gen_ratio"]
        / truth["NEvents"]
    )
    container['weighted_aeff'] = weighted_aeff.values.astype(FTYPE)
    return container