collisions across summary types.

*   When running on GPU (with cuDNN version 7.6.3 or
    later),`tf.nn.depthwise_conv2d` backprop to `filter` (and therefore also
    `tf.keras.layers.DepthwiseConv2D`) now operate deterministically (and
    `tf.errors.UnimplementedError` is no longer thrown) when op-determinism has

and a filter / kernel tensor of shape
`[filter_height, filter_width, in_channels, channel_multiplier]`, containing
`in_channels` convolutional filters of depth 1, `depthwise_conv2d` applies
a different filter to each input channel (expanding from 1 channel to
`channel_multiplier` channels for each), then concatenates the results