code: func (s *children) removeAt(index int) *node {
  	n := (*s)[index]
  	copy((*s)[index:], (*s)[index+1:])
  	(*s)[len(*s)-1] = nil
  	*s = (*s)[:len(*s)-1]
  	return n
  }
docs: // removeAt removes a value at a given index, pulling all subsequent values
  // back.