def __str__(self):
    return ((('Unification error: ' + self.message) + '\n') + str.join('\n', map((lambda p: ("In unification of '%s' and '%s'" % p)), self.unify_stack)))
def __str__(self):
    return ((('Unification error: ' + self.message) + '\n') + str.join('\n', map((lambda p: ("In unification of '%s' and '%s'" % p)), self.unify_stack)))