test
node1
BFO:0000003
occurrent
node1->node1
node4
BFO:0000015
process
node1->node4
node2
GO:0008152
metabolic process
node3
GO:0006807
nitrogen compound
metabolic process
node2->node3
node6
GO:0071941
nitrogen cycle
metabolic process
node3->node6
node5
GO:0008150
biological_process
node4->node5
node5->node2
node7
BFO:0000001
entity
node7->node1