  
          # Map the string representation of choices to the underlying value.
          # Allows us to deal with eg. integer choices while supporting either
          # integer or string input, but still get the correct datatype out.
          self.choice_strings_to_values = dict([
              (six.text_type(key), key) for key in self.choices.keys()
          ])
  
          self.allow_blank = kwargs.pop('allow_blank', False)
  
          super(ChoiceField, self).__init__(**kwargs)
  
 
</s> remove         ])
 </s> add         } </s> remove         field_names = set([
 </s> add         field_names = { </s> remove             unique_constraint_names |= set([
                model_field.unique_for_date,
                model_field.unique_for_month,
                model_field.unique_for_year
            ])
 </s> add             unique_constraint_names |= {model_field.unique_for_date, model_field.unique_for_month,
                                        model_field.unique_for_year} </s> remove     included = set((
        1,
        current - 1, current, current + 1,
        final
    ))
 </s> add     included = {1, current - 1, current, current + 1, final} </s> remove         unique_constraint_names -= set([None])
 </s> add         unique_constraint_names -= {None}
        self.choice_strings_to_values = {
            six.text_type(key): key for key in self.choices.keys()
        }
  
          # Map the string representation of choices to the underlying value.
          # Allows us to deal with eg. integer choices while supporting either
          # integer or string input, but still get the correct datatype out.
        self.choice_strings_to_values = {
            six.text_type(key): key for key in self.choices.keys()
        }
        self.choice_strings_to_values = {
            six.text_type(key): key for key in self.choices.keys()
        }
        self.choice_strings_to_values = {
            six.text_type(key): key for key in self.choices.keys()
        }
  
          self.allow_blank = kwargs.pop('allow_blank', False)
  
          super(ChoiceField, self).__init__(**kwargs)
  
keep keep keep keep replace replace replace keep keep keep keep keep
 Replaced all dict and set conversions from lists to dict and set literals. 
rest_framework/fields.py