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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def descriptions(self):
 """Human readable word descriptions."""

        descs = []
        for postag, form in zip(self.postags, self.forms):
            desc = VERB_TYPES.get(form, '')
            if len(desc) == 0:
                toks = form.split(' ')
                if len(toks) == 2:
                    plur_desc = PLURALITY.get(toks[0], None)
                    case_desc = CASES.get(toks[1], None)
                    toks = []
                    if plur_desc is not None:
                        toks.append(plur_desc)
                    if case_desc is not None:
                        toks.append(case_desc)
                    desc = ' '.join(toks)
            descs.append(desc)
        return descs