code: func (p *pathObject) Back(tag string) *pathObject {
  	np := p.clonePath().Back(tag)
  	return p.new(np)
  }
docs: // Back returns current path to a set of nodes on a given tag, preserving all constraints.
  //
  // If still valid, a path will now consider their vertex to be the same one as the previously tagged one,
  // with the added constraint that it was valid all the way here.
  // Useful for traversing back in queries and taking another route for things that have matched so far.
  //
  // Arguments:
  //
  // * `tag`: A previous tag in the query to jump back to.
  //
  // Example:
  // 	// javascript
  //	// Start from all nodes, save them into start, follow any status links,
  //	// jump back to the starting node, and find who follows them. Return the result.
  //	// Results are:
  //	//   {"id": "<alice>", "start": "<bob>"},
  //	//   {"id": "<charlie>", "start": "<bob>"},
  //	//   {"id": "<charlie>", "start": "<dani>"},
  //	//   {"id": "<dani>", "start": "<bob>"},
  //	//   {"id": "<dani>", "start": "<greg>"},
  //	//   {"id": "<dani>", "start": "<greg>"},
  //	//   {"id": "<fred>", "start": "<greg>"},
  //	//   {"id": "<fred>", "start": "<greg>"}
  //	g.V().Tag("start").Out("<status>").Back("start").In("<follows>").All()