Execution example::

  tokenize TokenBigram "Hello World"
  # [
  #   [
  #     0, 
  #     1337566253.89858, 
  #     0.000355720520019531
  #   ], 
  #   [
  #     {
  #       "position": 0, 
  #       "force_prefix": false, 
  #       "value": "He"
  #     }, 
  #     {
  #       "position": 1, 
  #       "force_prefix": false, 
  #       "value": "el"
  #     }, 
  #     {
  #       "position": 2, 
  #       "force_prefix": false, 
  #       "value": "ll"
  #     }, 
  #     {
  #       "position": 3, 
  #       "force_prefix": false, 
  #       "value": "lo"
  #     }, 
  #     {
  #       "position": 4, 
  #       "force_prefix": false, 
  #       "value": "o "
  #     }, 
  #     {
  #       "position": 5, 
  #       "force_prefix": false, 
  #       "value": " W"
  #     }, 
  #     {
  #       "position": 6, 
  #       "force_prefix": false, 
  #       "value": "Wo"
  #     }, 
  #     {
  #       "position": 7, 
  #       "force_prefix": false, 
  #       "value": "or"
  #     }, 
  #     {
  #       "position": 8, 
  #       "force_prefix": false, 
  #       "value": "rl"
  #     }, 
  #     {
  #       "position": 9, 
  #       "force_prefix": false, 
  #       "value": "ld"
  #     }, 
  #     {
  #       "position": 10, 
  #       "force_prefix": false, 
  #       "value": "d"
  #     }
  #   ]
  # ]
