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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def make_mapper(features):
 """Make a DataFrameMapper from a feature or list of features Args: features (Union[Feature, List[Feature]]):
 feature or list of features Returns: DataFrameMapper: mapper made from features """

    if not features:
        features = Feature(input=[], transformer=NullTransformer())
    if not iterable(features):
        features = (features, )
    return DataFrameMapper(
        [t.as_input_transformer_tuple() for t in features],
        input_df=True)