code: func (b *Builder) MovingAssignmentCount() int {
  	replicaCount := len(b.ring.ReplicaToPartitionToNode)
  	partitionCount := len(b.ring.ReplicaToPartitionToNode[0])
  	moving := 0
  	for replica := 0; replica < replicaCount; replica++ {
  		partitionToWait := b.ring.ReplicaToPartitionToWait[replica]
  		for partition := 0; partition < partitionCount; partition++ {
  			if partitionToWait[partition] > 0 {
  				moving++
  			}
  		}
  	}
  	return moving
  }
docs: // MovingAssignmentCount returns the number of assignments that are currently
  // "in motion". If you were to call IsMoving for every replica of every
  // partition and count the true responses, that would equal the
  // MovingAssignmentCount.