def getPriorities(request):
	"""
	Return: {string} 'priority' param value based on hierarchy: URL param value -> session (last used) -> none.
	"""
	filterVal = request.GET.getlist('priority', None)
	filterValLastUsed = request.session.get('filterPriorities', None)
	if not filterVal and filterValLastUsed:
		filterVal = filterValLastUsed
	return filterVal