def METHOD_NAME(obj, action):
	names = set()
	path_resolve = obj.path_resolve
	for fcu in action.fcurves:
		try:
			prop = path_resolve(fcu.data_path, False)
		except:
			prop = None
		if prop is not None:
			data = prop.data
			if isinstance(data, PoseBone):
				names.add(data.name)
	return names