docs: def __get_lowpoints(node, dfs_data):
      """Calculates the lowpoints for a single node in a graph."""
  
      ordering_lookup = dfs_data['ordering_lookup']
  
      t_u = T(node, dfs_data)
      sorted_t_u = sorted(t_u, key=lambda a: ordering_lookup[a])
      lowpoint_1 = sorted_t_u[0]
      lowpoint_2 = sorted_t_u[1]
  
      return lowpoint_1, lowpoint_2