Tokenizes single sentence and adds special BOS and EOS tokens.

        :param line: sentence

        returns: list representing tokenized sentence

def segment(self, line):
        """
        Tokenizes single sentence and adds special BOS and EOS tokens.

        :param line: sentence

        returns: list representing tokenized sentence
        """
        line = line.strip().split()
        entry = [self.tok2idx[i] for i in line]
        entry = [config.BOS] + entry + [config.EOS]
        return entry