      class EndOptionGroup(object):
          start_option_group = False
          end_option_group = True
  
      class Option(object):
          start_option_group = False
          end_option_group = False
  
          def __init__(self, value, display_text, disabled=False):
              self.value = value
 
</s> remove     class EndOptionGroup(object):
 </s> add     class EndOptionGroup: </s> remove     class StartOptionGroup(object):
 </s> add     class StartOptionGroup: </s> remove         class MockPager(object):
 </s> add         class MockPager: </s> remove             field.run_validation(u'slug-99-\u0420')
 </s> add             field.run_validation('slug-99-\u0420') </s> remove     class MockOriginalResponse(object):
 </s> add     class MockOriginalResponse:
    class Option:
      class EndOptionGroup(object):
          start_option_group = False
          end_option_group = True
  
    class Option:
          start_option_group = False
          end_option_group = False
  
          def __init__(self, value, display_text, disabled=False):
              self.value = value
keep keep keep keep replace keep keep keep keep keep
 Dropped Python 2 compatibility. (#6615)

Thanks to Jon Dufresne (@jdufresne) for review.

Co-authored-by: Asif Saif Uddin <auvipy@gmail.com>
Co-authored-by: Rizwan Mansuri <Rizwan@webbyfox.com> 
rest_framework/fields.py