code: def order(self):
      
      if not self.is_polynomial():
        raise AttributeError("Power needs to be positive integers")
      return max(key for key in self._data) if self._data else 0
docs: Finds the polynomial order.
  
      Examples
      --------
      >>> (x + 4).order
      1
      >>> (x + 4 - x ** 18).order
      18
      >>> (x - x).order
      0
      >>> (x ** -3 + 4).order
      Traceback (most recent call last):
        ...
      AttributeError: Power needs to be positive integers