def METHOD_NAME(self, THUMBNAIL):
    """Tests that sorl-thumbnail image field loads as expected."""
    THUMBNAIL.return_value = 'sorl-thumbnail'
    # Reload fields to re-declare the DynamicImageField
    self.clear_imports()
    self.mock_sorl_import()
    # Confirm inheritance from sorl-thubmnail ImageField
    image_field = fields.DynamicImageField()
    self.assertTrue(image_field.parent_class, 'sorl-thubmnail')