Clear the problem for Mktkn-0001.vdmsl
mk_token({1,2}) --> {1,2} in ProB --> mk_token({1,2}) in Overture Again.
But the case mk_token({}) does not work (Mktkn-0003.vdmsl).
I have to check the following cases:
mk_token([1,2]), mk_token([]), mk_token({1|->2, 3|->6}), mk_token({|->}), ...