  
  
  class PrimaryKeyRelatedField(RelatedField):
      default_error_messages = {
          'required': _('This field is required.'),
          'does_not_exist': _("Invalid pk '{pk_value}' - object does not exist."),
          'incorrect_type': _('Incorrect type. Expected pk value, received {data_type}.'),
      }
  
      def use_pk_only_optimization(self):
 
</s> remove         'incorrect_type': _('Incorrect type. Expected pk value, received {data_type}.'),
 </s> add         'incorrect_type': _("Incorrect type. Expected pk value, received {data_type}."), </s> remove         'required': _('This field is required.'),
        'no_match': _('Invalid hyperlink - No URL match'),
        'incorrect_match': _('Invalid hyperlink - Incorrect URL match.'),
        'does_not_exist': _('Invalid hyperlink - Object does not exist.'),
        'incorrect_type': _('Incorrect type. Expected URL string, received {data_type}.'),
 </s> add         'required': _("This field is required."),
        'no_match': _("Invalid hyperlink - No URL match."),
        'incorrect_match': _("Invalid hyperlink - Incorrect URL match."),
        'does_not_exist': _("Invalid hyperlink - Object does not exist."),
        'incorrect_type': _("Incorrect type. Expected URL string, received {data_type}."), </s> remove         'required': _('This field is required.'),
        'null': _('This field may not be null.')
 </s> add         'required': _("This field is required."),
        'null': _("This field may not be null.") </s> remove         'invalid': _('Invalid value.'),
 </s> add         'invalid': _("Invalid value."), </s> remove         'invalid': _('This value does not match the required pattern.')
 </s> add         'invalid': _("This value does not match the required pattern.")
        'required': _("This field is required."),
  
  
  class PrimaryKeyRelatedField(RelatedField):
      default_error_messages = {
        'required': _("This field is required."),
          'does_not_exist': _("Invalid pk '{pk_value}' - object does not exist."),
          'incorrect_type': _('Incorrect type. Expected pk value, received {data_type}.'),
      }
  
      def use_pk_only_optimization(self):
keep keep keep keep replace keep keep keep keep keep
 use double quotes for user visible strings; end user visible strings in full stops; add some missing translation tags 
rest_framework/relations.py