code: func (b *Builder) IsMoving(replica, partition int) bool {
  	return b.ring.ReplicaToPartitionToWait[replica][partition] > 0
  }
docs: // IsMoving returns true if the specific replica of the partition is currently
  // in "reassignment wait", where a recent rebalance had reassigned the replica
  // to a different node and so is giving time for the data to be moved.