Compute the log probability under the model.

def score(self, obs, pstates):
        """
        Compute the log probability under the model.
        """
        pstates_idx = np.array([self.e[p] for p in pstates])
        framelogprob = self._compute_log_likelihood(obs, pstates_idx)
        logprob, _ = self._do_forward_pass(framelogprob, pstates_idx)
        return logprob