def softmax_bw(softmax_output, label):
    """
    Cross entropy error with softmax output, backpropagation of deritivative w.r.t the inputs to the softmax function.
    dE/dzk = softmax_output_k - label_k
    :param softmax_output: Softmax output vector of length 10.
    :param label: One-hot encoded label vector of length 10. Example: [0 0 0 0 0 0 1 0 0 0] = 7
    :return: softmax_output - label
    """
    return softmax_output - label