Execution example::

  tokenize --tokenizer 'TokenNgram("unify_symbol", false)' --string "___---" --normalizer NormalizerAuto
  # [
  #   [
  #     0,
  #     1337566253.89858,
  #     0.000355720520019531
  #   ],
  #   [
  #     {
  #       "value": "__",
  #       "position": 0,
  #       "force_prefix": false,
  #       "force_prefix_search": false
  #     },
  #     {
  #       "value": "__",
  #       "position": 1,
  #       "force_prefix": false,
  #       "force_prefix_search": false
  #     },
  #     {
  #       "value": "_-",
  #       "position": 2,
  #       "force_prefix": false,
  #       "force_prefix_search": false
  #     },
  #     {
  #       "value": "--",
  #       "position": 3,
  #       "force_prefix": false,
  #       "force_prefix_search": false
  #     },
  #     {
  #       "value": "--",
  #       "position": 4,
  #       "force_prefix": false,
  #       "force_prefix_search": false
  #     },
  #     {
  #       "value": "-",
  #       "position": 5,
  #       "force_prefix": false,
  #       "force_prefix_search": false
  #     }
  #   ]
  # ]
