def rhyme_scheme(self):
        """
        Calculates the rhyme scheme of a given stanza. It doesn't yet support
        phonetical rhyming (homophones) and thus is still error-prone

        Example:
            >>> stanza = ['Ein rîchiu küneginne, frou Uote ir muoter hiez.', 'ir vater der hiez Dancrât, der in diu erbe liez', 'sît nâch sîme lebene, ein ellens rîcher man,', 'der ouch in sîner jugende grôzer êren vil gewan.']
            
            >>> S = Verse(stanza)
            
            >>> S.rhyme_scheme()
            'AABB'
        """
        rhymes = dict()
        i = 64
        strs = ""

        for line in self.syllabified:

            w = line[-1][-1][-3:]

            for r in rhymes.keys():
                if r.endswith(w) or w.endswith(r):
                    rhymes[w] = rhymes[r]
                    break

            if w in rhymes:
                strs += rhymes[w]
            else:
                i += 1
                rhymes[w] = chr(i)
                strs += chr(i)

        return strs