Relax the constraint that num_channels must be equal to 1 when we don't do frame stacking. This makes it easier to re-use the ATARI agent/network on other problems where observations have colors (e.g. DMLab).
Relax the constraint that num_channels must be equal to 1 when we don't
do frame stacking.
This makes it easier to re-use the ATARI agent/network on other problems
where observations have colors (e.g. DMLab).

PiperOrigin-RevId: 278326973

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