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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 _itertuples(df):
 """Custom implementation of ``DataFrame.itertuples`` that returns plain tuples instead of namedtuples. About 50% faster. """

    cols = [df.iloc[:, k] for k in range(len(df.columns))]
    return zip(df.index, *cols)