def _add_reference(reference, statement):
 (type_, value) = _expand_one_key_dictionary(reference)
 opt = Option(type_)
 param = SimpleParameter(value)
 opt.add_parameter(param)
 statement.add_child(opt)

def _add_reference ( reference , statement ) : ( type_ , value ) = _expand_one_key_dictionary ( reference ) opt = Option ( type_ ) param = SimpleParameter ( value ) opt . add_parameter ( param ) statement . add_child ( opt )
adds a reference to statement .