columns.dfy(8,0): Warning: module-level methods are always non-instance, so the 'static' keyword is not allowed here
columns.dfy(9,9): Error: assertion violation
Execution trace:
    (0,0): anon0
columns.dfy(10,11): Error: assertion violation
Execution trace:
    (0,0): anon0
columns.dfy(11,11): Error: assertion violation
Execution trace:
    (0,0): anon0

Dafny program verifier finished with 2 verified, 3 errors