test
node1
BFO:0000003
occurrent
node1->node1
node5
BFO:0000015
process
node1->node5
node2
GO:0043473
pigmentation
node3
GO:0048066
developmental
pigmentation
node2->node3
node4
GO:0048069
eye pigmentation
node3->node4
node6
GO:0008150
biological_process
node5->node6
node6->node2
node7
BFO:0000001
entity
node7->node1