bind 1 m1 : {v : Map_t Int Int | v = Map_default 0}
bind 2 s1 : {v : Set_Set Int | v = (Set_cup (Set_sng 10) (Set_sng 30))}
bind 3 m2 : {v : Map_t Int Int | v = (Map_store (Map_store m1 10 1) 20 1) } 

constraint:
  env [ 1; 2; 3 ]
  lhs {v : Set_Set Int | v = Map_to_set m2 }
  rhs {v : Set_Set Int | v = s1 } 
  id 1 tag []