docs: def add_issues_to_epic(self, epic_id, issue_keys, ignore_epics=True):
          """Add the issues in ``issue_keys`` to the ``epic_id``.
  
          :param epic_id: The ID for the epic where issues should be added.
          :type epic_id: int
          :param issue_keys: The issues to add to the epic
          :type issue_keys: str
          :param ignore_epics: ignore any issues listed in ``issue_keys`` that are epics. (Default: True)
          :type ignore_epics: bool
  
          """
          if self._options['agile_rest_path'] != GreenHopperResource.GREENHOPPER_REST_PATH:
              # TODO(ssbarnea): simulate functionality using issue.update()?
              raise NotImplementedError('JIRA Agile Public API does not support this request')
  
          data = {}
          data['issueKeys'] = issue_keys
          data['ignoreEpics'] = ignore_epics
          url = self._get_url('epics/%s/add' %
                              epic_id, base=self.AGILE_BASE_URL)
          return self._session.put(
              url, data=json.dumps(data))