code: func (p *Path) Except(path *Path) *Path {
  	np := p.clone()
  	np.stack = append(np.stack, exceptMorphism(path))
  	return np
  }
docs: // Except updates the current Path to represent the all of the current nodes
  // except those in the supplied Path.
  //
  // For example:
  //  // Will return []string{"B"}
  //  StartPath(qs, "A", "B").Except(StartPath(qs, "A"))