code: def equivalent(self, other):
          
          other = self.box(other)
          return self.node is other.node
docs: Return whether this BDD is equivalent to *other*.
  
          You can also use Python's ``is`` operator for BDD equivalency testing.
  
          For example::
  
             >>> a, b, c = map(bddvar, 'abc')
             >>> f1 = a ^ b ^ c
             >>> f2 = a & ~b & ~c | ~a & b & ~c | ~a & ~b & c | a & b & c
             >>> f1 is f2
             True