Add missing function def in tutorial

[konstantinbarkalov]

num_replace is used in process function few step later.

Otherwise it will fail on proccessing text with digits:

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-17-f80be2d2f8a4> in <module>
----> 1 output = process(process_pipeline, text='привет, как твои дела, засранец, 1000 лет не видел тебя', keep_pos=True, keep_punct=False)
      2 output

<ipython-input-10-5cbbe2657eda> in process(pipeline, text, keep_pos, keep_punct)
     52             if not named:
     53                 if pos == 'NUM' and token.isdigit():  # Заменяем числа на xxxxx той же длины
---> 54                     lemma = num_replace(token)
     55                 tagged_propn.append('%s_%s' % (lemma, pos))
     56             else:

NameError: name 'num_replace' is not defined

[akutuzov]

Thanks!