listNgramQuery = ['to machine learning problems',
    'introduction to machine learning', 'short introduction to machine',
    'very short introduction to', 'gives very short introduction',
    'document gives very short', 'this document gives very',
    'machine learning problems', 'to machine learning',
    'introduction to machine', 'short introduction to',
    'very short introduction', 'gives very short', 'document gives very',
    'this document gives', 'learning problems', 'machine learning',
    'to machine', 'introduction to', 'short introduction', 'very short',
    'gives very', 'document gives', 'this document', 'problems',
    'learning', 'machine', 'to', 'introduction', 'short', 'very',
    'gives', 'document', 'this']
Как получить словосочетания и ассоциации n-грамм в python nltk?