def get_shared_keys(param_list):
	"""
	For the given list of parameter dictionaries, return a list of the dictionary
	keys that appear in every parameter dictionary
	
	>>> get_shared_keys([{'a':0, 'b':1, 'c':2, 'd':3}, {'a':0, 'b':1, 'c':3}, {'a':0, 'b':'beta'}])
	['a', 'b']
	>>> get_shared_keys([{'a':0, 'd':3}, {'a':0, 'b':1, 'c':2, 'd':3}, {'a':0, 'b':1, 'c':2}])
	['a']
	"""
	if not param_list:
		return
	keys = set(param_list[0].keys())
	for i in range(1, len(param_list)):
		keys = keys.intersection(param_list[i].keys())
	keys = list(keys)
	keys.sort()
	return keys