'Sets up the ExpandableField with the collapsed and expanded versions of the serializer.'

def __init__(self, **kwargs):

    assert (('collapsed_serializer' in kwargs) and ('expanded_serializer' in kwargs))
    self.collapsed = kwargs.pop('collapsed_serializer')
    self.expanded = kwargs.pop('expanded_serializer')
    super(ExpandableField, self).__init__(**kwargs)
