Random tests
Testing for 'baal World What if Think squad what'
Traceback:
   in 
   in 
TypeError: gym_slang() takes exactly 1 argument (2 given)

As shown, when testing with random inputs, a second argument is being passed, and the default function declaration of

def gym_slang(phrase):

fails.

I captured the second argument and printed it, I got the following result:

Random tests
Testing for 'What world babylon Hello Combination I am world do not instagram world probably fake Fake Hello World gym babel'
()
([['i am', "i'm"], ['instagram', 'insta'], ['do not', "don't"], ['going to', 'gonna'], ['combination', 'combo']],)
Test Passed
Testing for 'Lorem Ipsum world baal Baal my crush Think Going to Crush wait Going to'
()
([['i am', "i'm"], ['instagram', 'insta'], ['do not', "don't"], ['going to', 'gonna'], ['combination', 'combo']],)
Test Passed
Testing for 'Do not was combination squad Lorem hello Probably If instagram Do not Do not Squad Hello wait hello Hello Probably Gym'
()
([['i am', "i'm"], ['instagram', 'insta'], ['do not', "don't"], ['going to', 'gonna'], ['combination', 'combo']],)
Test Passed

Hope this helps!

Some of the test cases pass an unexpected second argument to the function. The second arguments are not used, and it's easy enough to grab them with *args and then ignore them, but it shouldn't be passed in the first place.

All you really need to do is setup

class Node (object):
  pass