Support broadcasting

[wiso]

I have, let say, 2 electronic channels (actually many more). Each one returns an integer value between 0 and 15 (actually much more). In each event I have a variable ADC which is an array of lenght 2 (my two channels). I have nevents, so I have a matrix adcs nevents x 2 to be used to fill a 2D histogram.

Now I am doing:

axis_channel = hist.axis.Integer(0, 2 name="channel", label="Channel index")
axis_adc = hist.axis.Regular(16, 0, 16, name="adc")

histo = hist.Hist(axis_channel, axis_adc)

histo.fill(
            channel=np.repeat(np.arange(2)[np.newaxis, :], ak.num(adcs, axis=0), axis=0).flatten(),
            adc=ak.flatten(adcs),
        )

or using broadcasting

histo.fill(
            channel=np.broadcast_arrays([0, 1], adcs.T)[0],
            adc=ak.flatten(adcs),
        )

I would like to do

histo.fill(channel=[0, 1], adc=adcs)

this means that channels must broadcast to [[0, 1], [0, 1], ... ] and fill should support 2D inputs.