                  native = data[field_name]
          except KeyError:
              if self.default is not None and not self.partial:
                  # Note: partial updates shouldn't set defaults
                  if is_simple_callable(self.default):
                      native = self.default()
                  else:
                      native = self.default
              else:
                  if self.required:
                      raise ValidationError(self.error_messages['required'])
                  return
  
 
</s> remove             value = [] if self.many else None
 </s> add             value = self.get_default_value()
                native = self.get_default_value()
                  native = data[field_name]
          except KeyError:
              if self.default is not None and not self.partial:
                  # Note: partial updates shouldn't set defaults
                native = self.get_default_value()
                native = self.get_default_value()
                native = self.get_default_value()
                native = self.get_default_value()
              else:
                  if self.required:
                      raise ValidationError(self.error_messages['required'])
                  return
  
keep keep keep keep replace replace replace replace keep keep keep keep keep
 RelatedField default value handling fixed 
rest_framework/fields.py