def _convert_ITP_to_path_to_index(index_to_path):
	"""convert index_to_path pandas series to path_to_index dict 
	----
	index_to_path:(pandas.series)

	returns
	path_to_index:(dict) {path:[indices corresponding to that path]}
	"""
	path_to_index = dict()
	for i in index_to_path.index:
		index, path = i, index_to_path[i]
		if path in set(path_to_index.keys()):
			path_to_index[path].append(index)
		else:
			path_to_index.update({path:[index]})
	return path_to_index