def read_rules(rules):
	"""
	Read rules stored within file

	Params: 
		rules (str): path to rules file

	Returns: a dict of trigger: [candidates] representing rules for each use-case
	"""

	with open(rules, 'r') as file:
		lines = file.readlines()

	rules = {'colon': {}, 'cervix': {}, 'celiac': {}, 'lung': {}}
	for line in lines:
		trigger, candidates, position, mode, use_cases = line.strip().split('\t')
		use_cases = use_cases.split(',')
		for use_case in use_cases:
			rules[use_case][trigger] = (candidates.split(','), position, mode)
	return rules