+ return "Undefined. for <%s %s>" % (self.__class__.__name__, id(self))
+
+ def __str__(self):
+ return self.object_id()
+
+ def __repr__(self):
+ return '<%s>' % self.object_id()
+
+ def __hash__(self):
+ return hash(self.object_id())
+
+ def __eq__(self, other):
+ if not isinstance(other, self.__class__):
+ return NotImplemented
+ if other.object_id() == self.object_id():
+ return True
+ return False
+
+ # This can be removed when python2 support is dropped.
+ def __ne__(self, other):
+ return not self.__eq__(other)