[Python] How Trimesh face_adjacency works

I'm trying to get the two faces and two vertices that touch the edge.

import trimesh

mesh = trimesh.load_mesh('../demos/data/triangle_mesh.stl')

print(len(mesh.faces),len(mesh.vertices))

e = 10
print(mesh.edges[e])
f = mesh.face_adjacency[e]
print(f)
print(mesh.faces[f[0]])
print(mesh.faces[f[1]])


The output is

200 121
[ 7 26]
[4 5]
[7 8 9]
[ 7 9 25]


as you can see the endpoints of the edge are 7,26. But neither of the two faces contains 7 and 26. The two faces share a common edge, but its endpoints are 7,9. What is wrong with my logic?

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