code: func (it *Count) Next(ctx context.Context) bool {
  	if it.done {
  		return false
  	}
  	size, exact := it.it.Size()
  	if !exact {
  		for size = 0; it.it.Next(ctx); size++ {
  			for ; it.it.NextPath(ctx); size++ {
  			}
  		}
  	}
  	it.result = quad.Int(size)
  	it.done = true
  	return true
  }
docs: // Next counts a number of results in underlying iterator.