def add_gradients_summary(grads, name_prefix="", name_suffix="",
                          collection_key=None):
    """ add_gradients_summary.

    Add histogram summary for given gradients.

    Arguments:
        grads: A list of `Tensor`. The gradients to summarize.
        name_prefix: `str`. A prefix to add to summary scope.
        name_suffix: `str`. A suffix to add to summary scope.
        collection_key: `str`. A collection to store the summaries.

    Returns:
        The list of created gradient summaries.

    """

    # Add histograms for gradients.
    summ = []
    for grad, var in grads:
        if grad is not None:
            summ_name = format_scope_name(var.op.name, name_prefix,
                                          "Gradients/" + name_suffix)
            summ_exists = summary_exists(summ_name)
            if summ_exists is not None:
                tf.add_to_collection(collection_key, summ_exists)
                summ.append(summ_exists)
            else:
                summ.append(get_summary("histogram", summ_name, grad,
                                        collection_key))
    return summ
dataset/ETHPy150Open tflearn/tflearn/tflearn/summaries.py/add_gradients_summary/original