code: def add_edge(self, u, v):
          
          # ubin = self.find_root(u)
          ru = self.find_root(u)
          rv = self.find_root(v)
          ru = self.reroot(ru, u)
          rv = self.reroot(rv, v)
  
          ubin.set_child(vbin)
  
          pass
docs: self = EulerTourForest()
          self.add_node(1)
          self.add_node(2)
          u, v = 1, 2