code: def gradient(self):
          r
          func = self
  
          class FunctionalQuotientGradient(Operator):
  
              """Functional representing the gradient of ``f(.) / g(.)``."""
  
              def _call(self, x):
                  """Apply the functional to the given point."""
                  dividendx = func.dividend(x)
                  divisorx = func.divisor(x)
                  return ((1 / divisorx) * func.dividend.gradient(x) +
                          (- dividendx / divisorx**2) * func.divisor.gradient(x))
  
          return FunctionalQuotientGradient(self.domain, self.domain,
                                            linear=False)
docs: r"""Gradient operator of the functional.
  
          Notes
          -----
          The derivative is computed using the quotient rule:
  
          .. math::
              [\nabla (f / g)](p) = (g(p) [\nabla f](p) -
                                      f(p) [\nabla g](p)) / g(p)^2