code: def relation_get(attribute=None, unit=None, rid=None):
      
      try:
          if rid in relation_ids('cluster'):
              return leader_get(attribute, rid)
          else:
              raise NotImplementedError
      except NotImplementedError:
          return _relation_get(attribute=attribute, rid=rid, unit=unit)
docs: Attempt to use leader-get if supported in the current version of Juju,
      otherwise falls back on relation-get.
  
      Note that we only attempt to use leader-get if the provided rid is a peer
      relation id or no relation id is provided (in which case we assume we are
      within the peer relation context).