          memo[id(self)] = result
          result.validators = self.validators[:]
          return result
  
      def validate(self, value):
          if value in validators.EMPTY_VALUES and self.required:
              raise ValidationError(self.error_messages['required'])
  
      def run_validators(self, value):
          if value in validators.EMPTY_VALUES:
 
</s> remove             value = [] if self.many else None
 </s> add             value = self.get_default_value() </s> remove                 if is_simple_callable(self.default):
                    native = self.default()
                else:
                    native = self.default
 </s> add                 native = self.get_default_value()
    def get_default_value(self):
        if is_simple_callable(self.default):
            return self.default()
        return self.default

          memo[id(self)] = result
          result.validators = self.validators[:]
          return result
  
    def get_default_value(self):
        if is_simple_callable(self.default):
            return self.default()
        return self.default

      def validate(self, value):
          if value in validators.EMPTY_VALUES and self.required:
              raise ValidationError(self.error_messages['required'])
  
      def run_validators(self, value):
          if value in validators.EMPTY_VALUES:
keep keep keep add keep keep keep keep keep keep
 RelatedField default value handling fixed 
rest_framework/fields.py