def add_doc_names_as_metadata(self, doc_names):
        '''
        :param doc_names: array-like[str], document names of reach document
        :return: Corpus-like object with doc names as metadata. If two documents share the same name
        (doc number) will be appended to their names.
        '''
        if len(doc_names) != self.get_num_docs():
            raise Exception("The parameter doc_names contains %s elements. "
                            "It should have %s elements, one per document." % (len(doc_names), self.get_num_docs()))

        doc_names_counter = collections.Counter(np.array(doc_names))
        metafact = CSRMatrixFactory()
        metaidxstore = IndexStore()
        doc_id_uses = collections.Counter()
        for i in range(self.get_num_docs()):
            doc_id = doc_names[i]
            if doc_names_counter[doc_id] > 1:
                doc_id_uses[doc_id] += 1
                doc_name_idx = metaidxstore.getidx('%s (%s)' % (doc_id, doc_id_uses[doc_id]))
            else:
                doc_name_idx = metaidxstore.getidx(doc_id)
            metafact[i, i] = doc_name_idx
        return self.add_metadata(metafact.get_csr_matrix(), metaidxstore)