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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 _parse_values(values, extra=None):
 """ Utility function to flatten out args. For internal use only. :param values: list, tuple, or str :param extra: list or None :return: list """

    coerced = list(values)

    if coerced == values:
        values = coerced
    else:
        coerced = tuple(values)
        if coerced == values:
            values = list(values)
        else:
            values = [values]

    if extra:
        values.extend(extra)
    return values