'iter_options() should return a list of options and option groups.'

def test_iter_options(self):

    field = serializers.ChoiceField(choices=[('Numbers', ['integer', 'float']), ('Strings', ['text', 'email', 'url']), 'boolean'])
    items = list(field.iter_options())
    assert items[0].start_option_group
    assert (items[0].label == 'Numbers')
    assert (items[1].value == 'integer')
    assert (items[2].value == 'float')
    assert items[3].end_option_group
    assert items[4].start_option_group
    assert (items[4].label == 'Strings')
    assert (items[5].value == 'text')
    assert (items[6].value == 'email')
    assert (items[7].value == 'url')
    assert items[8].end_option_group
    assert (items[9].value == 'boolean')
