DM.flatten_channels() should return separate commands

[ehpor]

Preferably a dictionary.

See

catkit2/catkit2/testbed/proxies/bmc_dm.py

Lines 40 to 52 in 608e7b9

	def flatten_channels(self, channel_names):
	summed_command = 0
	if isinstance(channel_names, str):
	channel_names = [channel_names]
	# Get commands from channels, zero each channel, and sum commands
	for channel_name in channel_names:
	summed_command += getattr(self, channel_name).get_latest_frame().data
	self.apply_shape(channel_name, np.zeros(2 * self.num_actuators))
	# Return summed command (note that this is not a DM shape)
	return summed_command

and also in the DM base class #156.