Function find_sources 

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

Find all nodes that have an edge of predicate type pointing TO target_id.

Example: find_sources("func:a.py::foo", Calls, ...) finds all callers of foo.