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Just like we turn BUILD_LIST; COMPARE_OP (in) into a LOAD_CONST if all
the members are consts, we can do the same for BUILD_SET, instead
turning it into a LOAD_CONST of a frozenset. The following is the
bytecode that is current produced for each datastructure.
>>> dis.dis(lambda o: o in (1,2,3))
 1 0 LOAD_FAST 0 (o) 
 3 LOAD_CONST 3 ((1, 2, 3)) 
 6 COMPARE_OP 6 (in) 
 9 RETURN_VALUE 
>>> dis.dis(lambda o: o in [1,2,3])
 1 0 LOAD_FAST 0 (o) 
 3 LOAD_CONST 3 ((1, 2, 3)) 
 6 COMPARE_OP 6 (in) 
 9 RETURN_VALUE 
>>> dis.dis(lambda o: o in {1,2,3})
 1 0 LOAD_FAST 0 (o) 
 3 LOAD_CONST 0 (1) 
 6 LOAD_CONST 1 (2) 
 9 LOAD_CONST 2 (3) 
 12 BUILD_SET 3 
 15 COMPARE_OP 6 (in) 
 18 RETURN_VALUE