code: def add_metadata(self, metadata_matrix, meta_index_store):
          '''
          Returns a new corpus with a the metadata matrix and index store integrated.
  
          :param metadata_matrix: scipy.sparse matrix (# docs, # metadata)
          :param meta_index_store: IndexStore of metadata values
          :return: TermDocMatrixWithoutCategories
          '''
          assert isinstance(meta_index_store, IndexStore)
          assert len(metadata_matrix.shape) == 2
          assert metadata_matrix.shape[0] == self.get_num_docs()
          return self._make_new_term_doc_matrix(new_X=self._X,
                                                new_y=None,
                                                new_category_idx_store=None,
                                                new_y_mask=np.ones(self.get_num_docs()).astype(bool),
                                                new_mX=metadata_matrix,
                                                new_term_idx_store=self._term_idx_store,
                                                new_metadata_idx_store=meta_index_storef add_metadata(self, metadata_matrix, meta_index_store):
          '''
          Returns a new corpus with a the metadata matrix and index store integrated.
  
          :param metadata_matrix: scipy.sparse matrix (# docs, # metadata)
          :param meta_index_store: IndexStore of metadata values
          :return: TermDocMatrixWithoutCategories
          '''
          assert isinstance(meta_index_store, IndexStore)
          assert len(metadata_matrix.shape) == 2
          assert metadata_matrix.shape[0] == self.get_num_docs()
          return self._make_new_term_doc_matrix(new_X=self._X,
                                                new_y=None,
                                                new_category_idx_store=None,
                                                new_y_mask=np.ones(self.get_num_docs()).astype(bool),
                                                new_mX=metadata_matrix,
                                                new_term_idx_store=self._term_idx_store,
                                                new_metadata_idx_store=meta_index_store)
docs: Returns a new corpus with a the metadata matrix and index store integrated.
  
          :param metadata_matrix: scipy.sparse matrix (# docs, # metadata)
          :param meta_index_store: IndexStore of metadata values
          :return: TermDocMatrixWithoutCategories