get_related_lemmas function for 'student' returns noisy noun set

After running get_related_lemmas for 'student', the returned noun set is 
[u'student', u'studentship', u'studying', u'study', u'studiousness', u'studiousnesses', u'students', u'studentships', u'studyings', u'studies']

How can we limit this set to just [u'student']?