An integer or tuple/list of 3 integers: (pool_depth, pool_height,
pool_width) specifying the size of the pooling window. Can be a single
integer to specify the same value for all spatial dimensions.
strides
An integer or tuple/list of 3 integers, specifying the strides of
the pooling operation. Can be a single integer to specify the same value
for all spatial dimensions.
padding
A string. The padding method, either 'valid' or 'same'.
Case-insensitive.
data_format
A string. The ordering of the dimensions in the inputs.
channels_last (default) and channels_first are supported.
channels_last corresponds to inputs with shape (batch, depth, height,
width, channels) while channels_first corresponds to inputs with shape
(batch, channels, depth, height, width).