code: func (p *Path) LabelContextWithTags(tags []string, via ...interface{}) *Path {
  	np := p.clone()
  	np.stack = append(np.stack, labelContextMorphism(tags, via...))
  	return np
  }
docs: // LabelContextWithTags is exactly like LabelContext, except it tags the value
  // of the label used in the traversal with the tags provided.