Error with NLTK

[Astraport]

I try Exploring text data with NLTK from https://github.com/mikhailklassen/Mining-the-Social-Web-3rd-Edition/blob/master/notebooks/Chapter%205%20-%20Mining%20Text%20Files.ipynb
And I constantly get an error. What could be the reason? Thanks.
`---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
in
22
23 # Frequent collocations in the text (usually meaningful phrases)
---> 24 text.collocations()
25
26 # Frequency analysis for words of interest

~\Anaconda3\lib\site-packages\nltk\text.py in collocations(self, num, window_size)
442
443 collocation_strings = [
--> 444 w1 + " " + w2 for w1, w2 in self.collocation_list(num, window_size)
445 ]
446 print(tokenwrap(collocation_strings, separator="; "))

~\Anaconda3\lib\site-packages\nltk\text.py in (.0)
442
443 collocation_strings = [
--> 444 w1 + " " + w2 for w1, w2 in self.collocation_list(num, window_size)
445 ]
446 print(tokenwrap(collocation_strings, separator="; "))

ValueError: too many values to unpack (expected 2)`