CHEMROF	Sequence Types and Features Ontology	Source
http://purl.obolibrary.org/obo/SO_0000985	http://purl.org/gc/Double	LOOM
http://purl.obolibrary.org/obo/SO_0000984	http://purl.org/gc/Single	LOOM
http://purl.obolibrary.org/obo/SO_1000009	https://w3id.org/chemrof/ElementFamilyEnum#Transition	LOOM