MultiSets.dfy(177,10): Error: new number of occurrences might be negative
Execution trace:
    (0,0): anon0
    (0,0): anon4_Then
    (0,0): anon3
MultiSets.dfy(268,23): Error: assertion violation
Execution trace:
    (0,0): anon0
    (0,0): anon11_Then
    (0,0): anon3
    (0,0): anon12_Then
    (0,0): anon14_Else
MultiSets.dfy(291,15): Error: assertion violation
Execution trace:
    (0,0): anon0
    (0,0): anon8_Then
    (0,0): anon3
    (0,0): anon9_Else
MultiSets.dfy(158,2): Error BP5003: A postcondition might not hold on this return path.
MultiSets.dfy(157,14): Related location: This is the postcondition that might not hold.
Execution trace:
    (0,0): anon0
MultiSets.dfy(164,2): Error BP5003: A postcondition might not hold on this return path.
MultiSets.dfy(163,14): Related location: This is the postcondition that might not hold.
Execution trace:
    (0,0): anon0

Dafny program verifier finished with 34 verified, 5 errors
