text: 
  class C(object):
      @property
      def x(self):
          return self._x
  
      def __init__(self):
          self._x = None
  
      @x.setter
      def x(self, value):
          self._x = value
  
  c = C()
  print(c.x)
  del c.x
  
  c.x = 1