code: def unique_identities(cls, sh_db):
          
          try:
              for unique_identity in api.unique_identities(sh_db):
                  yield unique_identity
          except Exception as e:
              logger.debug("Unique identities not returned from SortingHat due to %s", str(e))
docs: List the unique identities available in SortingHat.
  
          :param sh_db: SortingHat database