Initialize the observation table.

def _init_table(self):
        """
        Initialize the observation table.
        """
        self.observation_table.sm_vector.append(self.epsilon)
        self.observation_table.smi_vector = [random.choice(self.alphabet)]
        self.observation_table.em_vector.append(self.epsilon)

        self._fill_table_entry(self.epsilon, self.epsilon)
        for s in self.observation_table.smi_vector:
            self._fill_table_entry(s, self.epsilon)