Function transitive_callers 

pub fn transitive_callers(
    target_id: &str,
    predicate: CodeEdgePredicate,
    max_depth: usize,
    nodes_batch: &RecordBatch,
    edges_batch: &RecordBatch,
) -> Vec<CodeNode>

Reverse transitive search — find all nodes that can reach target_id following edges of type predicate in reverse, up to max_depth hops.

Example: transitive_callers("func:a.py::foo", 3, ...) finds all functions that directly or indirectly call foo, up to 3 levels deep.