Function data_binding_requirement_key 

pub fn data_binding_requirement_key(
    node_id: &NodeId,
    input_name: &str,
) -> String

Return the stable wire key used to bind one node input to its external data requirement.

The node.input spelling is part of the V1 JSON contract. Because both coordinates may themselves contain ., callers that index more than one binding must still reject distinct coordinates that render to the same key instead of silently overwriting one of them.