code: def norm(self, x):
          
          return float(np.sqrt(self.inner(x, x).real))
docs: Calculate the norm of an element.
  
          This is the standard implementation using `inner`.
          Subclasses should override it for optimization purposes.
  
          Parameters
          ----------
          x1 : `LinearSpaceElement`
              Element whose norm is calculated.
  
          Returns
          -------
          norm : float
              The norm of the element.