)
 if not isinstance(,): 
  if not isinstance(,): 
  if not isinstance(,): 
  if not isinstance(,): 
  if not isinstance(,): 
  if not isinstance(,): 
  if isinstance(self.): 
  if isinstance(self.): 
  if isinstance(self.): 
  if isinstance(self.): 
  if isinstance(self.): 
  if self.is None : 
  raise ValueError()
  if self.is None : 
  self.= self.
  def(self,): 
   
 if self.is None : 
  self.= self.
 self.= self.
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