Computes the Swish activation function.
The tf.nn.swish operation uses a custom gradient to reduce memory usage.
Since saving custom gradients in SavedModel is currently not supported, and
one would not be able to use an exported TF-Hub module for fine-tuning, we
provide this wrapper that can allow to select whether to use the native
TensorFlow swish operation, or whether to use a customized operation that
has uses default TensorFlow gradient computation.
Tensor representing preactivation values.
The activation value.