def ctc_batch_cost(y_true, y_pred, input_length, label_length):
    """Runs CTC loss algorithm on each batch element.

    # Arguments
        y_true: tensor `(samples, max_string_length)`
            containing the truth labels.
        y_pred: tensor `(samples, time_steps, num_categories)`
            containing the prediction, or output of the softmax.
        input_length: tensor `(samples, 1)` containing the sequence length for
            each batch item in `y_pred`.
        label_length: tensor `(samples, 1)` containing the sequence length for
            each batch item in `y_true`.

    # Returns
        Tensor with shape (samples,1) containing the
            CTC loss of each element.
    """
    raise NotImplementedError('MXNet Backend: CTC is not supported yet.')
