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

Created at: May 24, 2016, 7:49 p.m.; Updated at: May 24, 2016, 8:48 p.m.