code: def derivativeY(self,x,y):
          '''
          Evaluate the first derivative with respect to y of the function at given
          state space points.
  
          Parameters
          ----------
          x : np.array
               First input values.
          y : np.array
               Second input values; should be of same shape as x.
  
          Returns
          -------
          dfdy_out : np.array
              First derivative of function with respect to the second input,
              evaluated at (x,y), of same shape as inputs.
          '''
          xShift,xShiftDer = self.lowerBound.eval_with_derivative(y)
          dfdy_out = self.func.derivativeY(x-xShift,y) - xShiftDer*self.func.derivativeX(x-xShift,y)
          return dfdy_ouf derivativeY(self,x,y):
          '''
          Evaluate the first derivative with respect to y of the function at given
          state space points.
  
          Parameters
          ----------
          x : np.array
               First input values.
          y : np.array
               Second input values; should be of same shape as x.
  
          Returns
          -------
          dfdy_out : np.array
              First derivative of function with respect to the second input,
              evaluated at (x,y), of same shape as inputs.
          '''
          xShift,xShiftDer = self.lowerBound.eval_with_derivative(y)
          dfdy_out = self.func.derivativeY(x-xShift,y) - xShiftDer*self.func.derivativeX(x-xShift,y)
          return dfdy_out
docs: Evaluate the first derivative with respect to y of the function at given
          state space points.
  
          Parameters
          ----------
          x : np.array
               First input values.
          y : np.array
               Second input values; should be of same shape as x.
  
          Returns
          -------
          dfdy_out : np.array
              First derivative of function with respect to the second input,
              evaluated at (x,y), of same shape as inputs.