code: def print_block_num_row(block_num, cliques, next_cliques):
      
      n_cliques = len(cliques)
      if n_cliques == 0:
          print('|  {}'.format(block_num))
          return
  
      def mapper(clique):
          block_id, _ = clique
          if block_id not in next_cliques:
              return ' '
          return '|'
  
      format_str = '{:<' + str(n_cliques * 2) + '} {}'
      branches = list(map(mapper, cliques))
      for end in ('', block_num):
          print(format_str.format(' '.join(branches), end))
docs: Print out a row of padding and a row with the block number. Includes
      the branches prior to this block number.