I suppose so.
How about for an mxnx3 array `I` we have them set all values along the third dimension to 0 if they are all less than something like `.1`. Then we can say this sort of operation could be used to set relatively dark pixels to be black.
Two of several possible solutions are:

`I * (I.max(axis=2, keepdims=True) < .1)`

`I * (I.max(axis=2) < .1).reshape((I.shape[0], I.shape[1], 1))`

The former is preferable, but the latter is more likely.
We could encourage them to do the former by hinting that they should look up the `keepdims` keword argument.