          unique_constraint_names = set()
  
          for model_field in model_fields.values():
              # Include each of the `unique_for_*` field names.
              unique_constraint_names |= set([
                  model_field.unique_for_date,
                  model_field.unique_for_month,
                  model_field.unique_for_year
              ])
  
          unique_constraint_names -= set([None])
  
          # Include each of the `unique_together` field names,
          # so long as all the field names are included on the serializer.
 
</s> remove         unique_constraint_names -= set([None])
 </s> add         unique_constraint_names -= {None} </s> remove         field_names = set([
 </s> add         field_names = { </s> remove         ])
 </s> add         } </s> remove         ])
 </s> add         } </s> remove         return dict([
            (key, value if isinstance(value, list) else [value])
 </s> add         return {
            key: value if isinstance(value, list) else [value]
            unique_constraint_names |= {model_field.unique_for_date, model_field.unique_for_month,
                                        model_field.unique_for_year}
          unique_constraint_names = set()
  
          for model_field in model_fields.values():
              # Include each of the `unique_for_*` field names.
            unique_constraint_names |= {model_field.unique_for_date, model_field.unique_for_month,
                                        model_field.unique_for_year}
            unique_constraint_names |= {model_field.unique_for_date, model_field.unique_for_month,
                                        model_field.unique_for_year}
            unique_constraint_names |= {model_field.unique_for_date, model_field.unique_for_month,
                                        model_field.unique_for_year}
            unique_constraint_names |= {model_field.unique_for_date, model_field.unique_for_month,
                                        model_field.unique_for_year}
            unique_constraint_names |= {model_field.unique_for_date, model_field.unique_for_month,
                                        model_field.unique_for_year}
  
          unique_constraint_names -= set([None])
  
          # Include each of the `unique_together` field names,
          # so long as all the field names are included on the serializer.
keep keep keep keep replace replace replace replace replace keep keep keep keep keep
 Replaced all dict and set conversions from lists to dict and set literals. 
rest_framework/serializers.py