Function function_to_graph_view 

pub fn function_to_graph_view(function: &FunctionProto) -> GraphProto

Build a GraphProto view from a FunctionProto’s body - most compiler passes operate on a GraphProto per docs/COMPILER.md, and the engine’s backend-subgraph dispatcher needs the same view

The view resolves function.input / output (which are repeated string at the FunctionProto level) into ValueInfoProtos by looking up the matching entry in function.value_info. Missing entries surface as ValueInfoProto { name, ..default() }; the compiler’s validate pass then catches them as MissingTypeInfo.