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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 uniquecols(df):
 """ Return unique columns This is used for figuring out which columns are constant within a group """

    bool_idx = df.apply(lambda col: len(np.unique(col)) == 1, axis=0)
    df = df.loc[:, bool_idx].iloc[0:1, :].reset_index(drop=True)
    return df