Not passing the test

Hi, I really don't understand why this isn't correct. Can someone help me?

def boolean(x, y, operation):
if x == 1 and y == 1:
    if operation == "exclusive":
        return 0
    else:
        return 1
elif x == 0 and y == 0:
    if operation == "implication" or operation == "equivalence":
        return 1
    else:
        return 0
else:
    if operation == "conjuction" or operation == "equivalence":
        return 0
    else:
        return 1