{ instance: 'R', i: 10, c: 'a' }
{ instance: 'R', i: 20, c: 'a' }
{ instance: 'R', i: 123, c: 'b' }
{ instance: 'R', i: 1, c: 'a' }
1
"a"
{ instance: 'R', i: 2, c: 'b' }
{ instance: 'R', c: 'b' }
{ instance: 'R', i: 3, c: 'c' }
{ instance: 'S', slot1: 1, slot2: 'a' }
{ instance: 'X', _x1: 1, _x2: 2 }
{ instance: 'X', _x1: 1, _x2: 2 }