fields.DateTime - load/dump to timestamp

I'm currently using this code to parse/dump timestamp, but I believe this should be in standard library. Should I create pull request, or have I missed another way to work with datetime/timestamp format?

class DateTime(ma.fields.DateTime):
    """
    Class extends marshmallow standart DateTime with "timestamp" format.
    """

    DATEFORMAT_SERIALIZATION_FUNCS = \
        ma.fields.DateTime.DATEFORMAT_SERIALIZATION_FUNCS.copy()
    DATEFORMAT_DESERIALIZATION_FUNCS = \
        ma.fields.DateTime.DATEFORMAT_DESERIALIZATION_FUNCS.copy()

    DATEFORMAT_SERIALIZATION_FUNCS['timestamp'] = lambda x: x.timestamp()
    DATEFORMAT_DESERIALIZATION_FUNCS['timestamp'] = datetime.fromtimestamp