Function encode_binding_value 

pub fn encode_binding_value(
    role: &str,
    type_name: &str,
    slot_id_or_neg1: i64,
) -> String

Encode a binding’s (role, TYPE_NAME, slot_id_or_neg1) triple into the pipe-delimited value "<role>|<TYPE_NAME>|<slot_id_or_-1>". Reads inversely via parse_binding_value.