def add_sequence(self, words):
n = self.n<EOL>words = ['<STR_LIT>',] * (n-<NUM_LIT:1>) + words<EOL>for i in range(len(words)-n):<EOL><INDENT>self.add(tuple(words[i:i+n]))<EOL><DEDENT>
Add each of the tuple words[i:i+n], using a sliding window.
        Prefix some copies of the empty word, '', to make the start work.