m._compute_ambig_ll() -- Extend log-likelihood matrix to include ambiguity codes
                                 e.g.  What the score of a 'S'?  Here we use the max of C and G.

def _compute_ambig_ll(self):
        """
        m._compute_ambig_ll() -- Extend log-likelihood matrix to include ambiguity codes
                                 e.g.  What the score of a 'S'?  Here we use the max of C and G.
        """
        for Dll in self.ll:
            for L in one2two.keys():
                Dll[L] = max(Dll[one2two[L][0]],  Dll[one2two[L][1]] )
            Dll['N'] = 0.0
            Dll['B'] = 0.0