An absurd recursive lambda expression to recurse up the DAG, finding a Camera2 node

find_camera_expr.nk

set cut_paste_input [stack 0]
version 6.2 v3
push $cut_paste_input
Axis2 {
 name Axis1
 selected true
 xpos -107
 ypos -135
}
Camera2 {
 name Camera1
 label "\[value focal]"
 selected true
 xpos -107
 ypos -55
}
Dot {
 name Dot1
 selected true
 xpos -83
 ypos 44
}
Dot {
 name Dot4
 selected true
 xpos -83
 ypos 71
}
set N1dec72f0 [stack 0]
Scene {
 name TopNode
 label "\[value find_focal]\nOnly works when Axis is disconnected"
 selected true
 xpos -26
 ypos 115
 addUserKnob {20 User}
 addUserKnob {7 find_focal}
 find_focal {{"\[topnode].focal"}}
}
push $N1dec72f0
Scene {
 name AbsurdExpression
 label "\[value find_focal]"
 selected true
 xpos -192
 ypos 115
 addUserKnob {20 User}
 addUserKnob {7 find_focal}
 find_focal {{"\[python \{(  lambda n: (lambda f, n: f(f, n)) (lambda f, n: f(f, n.input(0)) if n.Class()!=\"Camera2\" else n, n)  )(nuke.thisNode())\['focal'].value()\}]" i}}
}