code: def find(self, node_label):
          
          queue = []
          current_node = node_label
          while self.__forest[current_node] >= 0:
              queue.append(current_node)
              current_node = self.__forest[current_node]
          root_node = current_node
  
          # Path compression
          for n in queue:
              self.__forest[n] = root_node
  
          return root_node
docs: Finds the set containing the node_label.
          Returns the set label.