def is_negation(bigram_first_word):
	"""Gets the fist word of a bigram and checks if this words is a negation or contraction word"""

	NEGATION_WORDS = ['no','not']
	NEGATION_CONTRACTIONS = ["isn't","aren't","wasn't","weren't","haven't",
								"hasn't","hadn't","won't","wouldn't","don't",
								"doesn't","didn't","can't","couldn't","shouldn't"
								"mightn't","mustn't","ain't","mayn't","oughtn't",
								"shan't"]

	return (bigram_first_word in NEGATION_WORDS) or (bigram_first_word in NEGATION_CONTRACTIONS)