code: func (p *Path) InPredicates() *Path {
  	np := p.clone()
  	np.stack = append(np.stack, predicatesMorphism(true))
  	return np
  }
docs: // InPredicates updates this path to represent the nodes of the valid inbound
  // predicates from the current nodes.
  //
  // For example:
  //  // Returns a list of predicates valid from "bob"
  //  //
  //  // Will return []string{"follows"} if there are any things that "follow" Bob
  //  StartPath(qs, "bob").InPredicates()