code: def install_traversals(cls, node_set):
      
      rels = cls.defined_properties(rels=True, aliases=False, properties=False)
  
      for key, value in rels.items():
          if hasattr(node_set, key):
              raise ValueError("Can't install traversal '{0}' exists on NodeSet".format(key))
  
          rel = getattr(cls, key)
          rel._lookup_node_class()
  
          traversal = Traversal(source=node_set, name=key, definition=rel.definition)
          setattr(node_set, key, traversal)
docs: For a StructuredNode class install Traversal objects for each
      relationship definition on a NodeSet instance