'Transform the *outgoing* native value into primitive data.'

def to_representation(self, value):

    raise NotImplementedError(u'{cls}.to_representation()    must    be    implemented    for    field    {field_name}.    If    you    do    not    need    to    support    write    operations    you    probably    want    to    subclass    `ReadOnlyField`    instead.'.format(cls=self.__class__.__name__, field_name=self.field_name))
