code: def skipgram_fasttext_batch(centers, contexts, num_tokens, subword_lookup,
                              dtype, index_dtype):
      
      contexts = mx.nd.array(contexts[2], dtype=index_dtype)
      data, row, col = subword_lookup(centers)
      centers = mx.nd.array(centers, dtype=index_dtype)
      centers_csr = mx.nd.sparse.csr_matrix(
          (data, (row, col)), dtype=dtype,
          shape=(len(centers), num_tokens))  # yapf: disable
      return centers_csr, contexts, centers
docs: Create a batch for SG training objective with subwords.