def METHOD_NAME(data: pd.DataFrame, target: str, group_cols: List):
    differencers = {}
    grouped = data.groupby(by=group_cols) if group_cols else data.groupby(lambda x: True)
    for group, subset in grouped:
        differencer = Differencer()
        differencer.fit(subset[target].values)
        differencers[group] = differencer
    return differencers