def modifierMask( self ):
		try:
			return 0
		except Exception as e:
			self.logToConsole( "modifierMask: %s" % str(e) )
Use any combination of these to determine the modifier keys for your default shortcut:
dataset/ETHPy150Open Tosche/BubbleKern/ShowKernBubbles.glyphsReporter/Contents/Resources/ShowKernBubbles.py/ShowKernBubbles.modifierMask