An integer or tuple/list of 2 integers: (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 2 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, height, width, channels) while channels_first corresponds to
inputs with shape (batch, channels, height, width).