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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 change_default( kls, key, new_default, new_converter=None, new_reference_value=None, ):
 """return a new configman Option object that is a copy of an existing one, giving the new one a different default value"""

    an_option = kls.get_required_config()[key].copy()
    an_option.default = new_default
    if new_converter:
        an_option.from_string_converter = new_converter
    if new_reference_value:
        an_option.reference_value_from = new_reference_value
    return an_option