def __init__(self, window=<NUM_LIT:4>, std_coeff=<NUM_LIT>, tokenizer=EnglishTokenizer()):
self.window = window<EOL>self.sim = None<EOL>self.rank = None<EOL>self.sm = None<EOL>self.std_coeff = std_coeff<EOL>self.tokenizer = tokenizer<EOL>
window: int, window size for local similarity ranking
std_coeff: double, threshold to determine boundary, see paper for more details
tokenizer: an object with tokenize() method,
           which takes a string as argument and return a sequence of tokens.