code: def proximal(self):
          
          if self.quadratic_coeff < 0:
              raise TypeError('`quadratic_coeff` {} must be non-negative'
                              ''.format(self.quadratic_coeff))
  
          return proximal_quadratic_perturbation(
              self.functional.proximal,
              a=self.quadratic_coeff, u=self.linear_term)
docs: Proximal factory of the quadratically perturbed functional.