import tensorflow as tf


    Run ``sess.run(tf.global_variables_initializer())`` for TF 0.12+ or
    ``sess.run(tf.initialize_all_variables())`` for TF 0.11.

    Parameters
    ----------
    sess : Session
        TensorFlow session.

    """
    assert sess is not None
    # try:    # TF12+
    sess.run(tf.global_variables_initializer())
    # except: # TF11
    #     sess.run(tf.initialize_all_variables())


class Layer(object):
    """The basic :class:`Layer` class represents a single layer of a neural network.

    It should be subclassed when implementing new types of layers.
    Because each layer can keep track of the layer(s) feeding into it, a
    network's output :class:`Layer` instance can double as a handle to the full
    network.
