code: func (t *Tracker) AttachTo(parent *Tracker) {
  	if t.parent != nil {
  		t.parent.remove(t)
  	}
  	parent.mu.Lock()
  	parent.mu.children = append(parent.mu.children, t)
  	parent.mu.Unlock()
  
  	t.parent = parent
  	t.parent.Consume(t.BytesConsumed())
  }
docs: // AttachTo attaches this memory tracker as a child to another Tracker. If it
  // already has a parent, this function will remove it from the old parent.
  // Its consumed memory usage is used to update all its ancestors.