@Override
    public int getOpCode() {
        return OP_CODE;
    }
Generic Default Transition Time Set is an acknowledged message used to set the Generic Default Transition Time state of an element (see Section 3.1.3).
The response to the Generic Default Transition Time Set message is a Generic Default Transition Time Status message.

@param appKey         the appkey
@param genericTransitionTime The value of the Generic Default Transition Time state.
mesh/src/main/java/no/nordicsemi/android/mesh/transport/GenericDefaultTransitionTimeSet.java