docs: def pfmerge(self, dest, *sources):
          """
          Merge N different HyperLogLogs into a single one.
  
          :param dest:
          :param sources:
          :return:
          """
          sources = [self.redis_key(k) for k in sources]
          with self.pipe as pipe:
              return pipe.pfmerge(self.redis_key(dest), *sources)