'If `allow_null=True` then \'\' on HTML forms is treated as None.'

def test_allow_null(self):

    field = serializers.ChoiceField(allow_null=True, choices=[1, 2, 3])
    field.field_name = 'example'
    value = field.get_value(QueryDict('example='))
    assert (value is None)
    output = field.run_validation(None)
    assert (output is None)
