Function protocol_descriptor_with 

pub fn protocol_descriptor_with(
    protocol: &ProtocolItem,
    imported: &TypeTable,
) -> Result<ProtocolDescriptor>

protocol_descriptor for the protocol of a module, which may also use the value types of the protocols of the modules it depends on: imported. Each it uses is copied into its own table, with the types that one uses in turn, so the descriptor stays self-contained.