Function check_graph 

pub fn check_graph(
    engine: &Engine,
    graph: &NodeGraph,
    branches: &Branches,
    resolved: &HashMap<String, ResolvedInput>,
) -> Result<CheckedGraph, DagError>

Typecheck a graph. resolved must already contain one entry per node in graph.nodes, in the same order — building that mapping (via pipeline::resolve_and_load, one call per node) is the caller’s job (a later task), same division of responsibility pipeline::check already has.