code: def _get_entries_for_calculation(self):
          
          mgr = self._get_provider_manager('Grading')  # what about the Proxy?
          if not mgr.supports_gradebook_column_lookup():
              raise errors.OperationFailed('Grading does not support GradebookColumn lookup')
          gradebook_id = Id(self._my_map['assignedGradebookIds'][0])
          lookup_session = mgr.get_grade_entry_lookup_session_for_gradebook(gradebook_id,
                                                                            proxy=getattr(self, "_proxy", None))
          entries = lookup_session.get_grade_entries_for_gradebook_column(self.get_gradebook_column_id())
          return [e for e in entries if not e.is_ignored_for_calculations()]
docs: Ignores entries flagged with ignoreForCalculation