  
          # Standard case, return the object instance.
          return get_attribute(instance, self.source_attrs)
  
      @property
      def choices(self):
          queryset = self.get_queryset()
          if queryset is None:
              # Ensure that field.choices returns something sensible
              # even when accessed with a read-only field.
              return {}
 
</s> remove         return self.child_relation.choices
 </s> add         return self.get_choices() </s> remove             self.grouped_choices,
 </s> add             self.get_choices(cutoff=self.html_cutoff),
    def get_choices(self, cutoff=None):
  
          # Standard case, return the object instance.
          return get_attribute(instance, self.source_attrs)
  
    def get_choices(self, cutoff=None):
    def get_choices(self, cutoff=None):
          queryset = self.get_queryset()
          if queryset is None:
              # Ensure that field.choices returns something sensible
              # even when accessed with a read-only field.
              return {}
keep keep keep keep replace replace keep keep keep keep keep
 Limit queryset when rendering relational choices. (#4375)

Limit querysets to html_cutoff when rendering relational choices 
rest_framework/relations.py