code: def list_groups(self, filtr=None):
          
          self.project_service.set_auth(self._token_project)
          return self.project_service.list_groups(filtr)
docs: Get the groups the logged in user is a member of.
  
          Optionally filter by 'member' or 'maintainer'.
  
          Args:
              filtr (optional[string|None]): ['member'|'maintainer']
  
          Returns:
              (list[string]): List of group names.
  
          Raises:
              requests.HTTPError on failure.