How to use the elementpath.datatypes.GregorianMonthDay function in elementpath

'name': XSD_GDAY,
        'python_type': (unicode_type, str, datatypes.GregorianDay),
        'admitted_facets': DATETIME_FACETS,
        'facets': [COLLAPSE_WHITE_SPACE_ELEMENT],
        'to_python': datatypes.GregorianDay.fromstring,
    },  # DD
    {
        'name': XSD_GMONTH,
        'python_type': (unicode_type, str, datatypes.GregorianMonth),
        'admitted_facets': DATETIME_FACETS,
        'facets': [COLLAPSE_WHITE_SPACE_ELEMENT],
        'to_python': datatypes.GregorianMonth.fromstring,
    },  # MM
    {
        'name': XSD_GMONTH_DAY,
        'python_type': (unicode_type, str, datatypes.GregorianMonthDay),
        'admitted_facets': DATETIME_FACETS,
        'facets': [COLLAPSE_WHITE_SPACE_ELEMENT],
        'to_python': datatypes.GregorianMonthDay.fromstring,
    },  # MM-DD
    {
        'name': XSD_TIME,
        'python_type': (unicode_type, str, datatypes.Time),
        'admitted_facets': DATETIME_FACETS,
        'facets': [COLLAPSE_WHITE_SPACE_ELEMENT],
        'to_python': datatypes.Time.fromstring,
    },  # hh:mm:ss
    {
        'name': XSD_DURATION,
        'python_type': (unicode_type, str, datatypes.Duration),
        'admitted_facets': FLOAT_FACETS,
        'facets': [COLLAPSE_WHITE_SPACE_ELEMENT],

'facets': [COLLAPSE_WHITE_SPACE_ELEMENT],
        'to_python': datatypes.GregorianDay.fromstring,
    },  # DD
    {
        'name': XSD_GMONTH,
        'python_type': (unicode_type, str, datatypes.GregorianMonth),
        'admitted_facets': DATETIME_FACETS,
        'facets': [COLLAPSE_WHITE_SPACE_ELEMENT],
        'to_python': datatypes.GregorianMonth.fromstring,
    },  # MM
    {
        'name': XSD_GMONTH_DAY,
        'python_type': (unicode_type, str, datatypes.GregorianMonthDay),
        'admitted_facets': DATETIME_FACETS,
        'facets': [COLLAPSE_WHITE_SPACE_ELEMENT],
        'to_python': datatypes.GregorianMonthDay.fromstring,
    },  # MM-DD
    {
        'name': XSD_TIME,
        'python_type': (unicode_type, str, datatypes.Time),
        'admitted_facets': DATETIME_FACETS,
        'facets': [COLLAPSE_WHITE_SPACE_ELEMENT],
        'to_python': datatypes.Time.fromstring,
    },  # hh:mm:ss
    {
        'name': XSD_DURATION,
        'python_type': (unicode_type, str, datatypes.Duration),
        'admitted_facets': FLOAT_FACETS,
        'facets': [COLLAPSE_WHITE_SPACE_ELEMENT],
        'to_python': datatypes.Duration.fromstring,
    },  # PnYnMnDTnHnMnS