def cbow_batch(centers, contexts, num_tokens, dtype, index_dtype):
contexts_data, contexts_row, contexts_col = contexts<EOL>centers = mx.nd.array(centers, dtype=index_dtype)<EOL>contexts = mx.nd.sparse.csr_matrix(<EOL>(contexts_data, (contexts_row, contexts_col)),<EOL>dtype=dtype, shape=(len(centers), num_tokens))  <EOL>return centers, contexts<EOL>
Create a batch for CBOW training objective.