Small bug in questiongenerator code (pool should be list)

[sujitpal]

My environment:

• MacOS Monterey 12.6.5
• Python 3.11.4

Running the following code (as shown in README):

qg = QuestionGenerator()
text = "..."
response = qg.generate(text, num_questions=5)
print(response)

returns the following error:

...
  File "/Users/palsujit/Projects/hgraph-sujitpal/llamaindex-apollo-preprocessing/src/../external/question_generator/questiongenerator.py", line 250, in _get_MC_answers
    choices.extend(random.sample(pool, num_choices - len(choices)))
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/random.py", line 439, in sample
    raise TypeError("Population must be a sequence.  "
TypeError: Population must be a sequence.  For dicts or sets, use sorted(d).

It seems to be because pool is a set and random.sample expects a list, so I updated line 249 of questiongenerator.py to read:

pool = list(pool.difference(set(choices)))

and this seems to have fixed it.