Function pass_through 

pub fn pass_through(g: &mut Graph, input: Output) -> Output

Record a PassThrough syscall NodeProto into a Graph.

The framework’s structural identity op - threads a value through a partition without doing any compute. Authors reach for it when a partition needs a non-wire node (e.g. a receiver class that only forwards values it receives over the wire). The recorded NodeProto’s home class is inferred by the compiler from the input’s home.