iam getting error while executing code that grandchild has no attribute parent

Question

class parent():
  def father(self):
    return ("father house")
  def father2(self):
    return ("father2 house")
class child(parent):
  def child(self):
    return ("child house")
class grandchild(child):
  def grandchild(self):
    return ("grandchild house")

#AttributeError: 'grandchild' object has no attribute 'parent'