def ARGMIN(agg_column, out_column):
    """
    Builtin arg minimum aggregator for groupby

    Example: Get the movie with minimum rating per user.

    >>> sf.groupby("user",
    ...            {'best_movie':tc.aggregate.ARGMIN('rating','movie')})
    """
    return '__builtin__argmin__', [agg_column, out_column]
