Comprehensions.dfy(12,13): Error: assertion violation
Execution trace:
    (0,0): anon0
    (0,0): anon9_Then
    (0,0): anon10_Then
    (0,0): anon4
    (0,0): anon11_Then
    (0,0): anon12_Then
    (0,0): anon8

Dafny program verifier finished with 6 verified, 1 error