def generate_text(self, generation_type='markov'):
        """ Generates sentences from a given corpus
        Args:
            generation_type: 'markov' | 'hmm' | 'hmm_past'
        Returns:
            Properly formatted string of generated sentences
        """
        assert generation_type in ['markov', 'hmm', 'hmm_past']
        if generation_type == "markov":
            return self._text_generator(next_token=self._generate_next_token)
        elif generation_type == "hmm":
            return self._text_generator(next_token=self._generate_next_token_hmm, emit=self._emitHMM)
        elif generation_type == "hmm_past":
            return self._text_generator(next_token=self._generate_next_token_hmm, emit=self._emitHMM_with_past)