code: def derivativeZ(self,x,y,z):
          '''
          Evaluate the first derivative with respect to z 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.
          z : np.array
               Third input values; should be of same shape as x.
  
          Returns
          -------
          dfdz_out : np.array
              First derivative of function with respect to the third input,
              evaluated at (x,y,z), of same shape as inputs.
          '''
          xShift = self.lowerBound(y)
          dfdz_out = self.func.derivativeZ(x-xShift,y,z)
          return dfdz_ouf derivativeZ(self,x,y,z):
          '''
          Evaluate the first derivative with respect to z 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.
          z : np.array
               Third input values; should be of same shape as x.
  
          Returns
          -------
          dfdz_out : np.array
              First derivative of function with respect to the third input,
              evaluated at (x,y,z), of same shape as inputs.
          '''
          xShift = self.lowerBound(y)
          dfdz_out = self.func.derivativeZ(x-xShift,y,z)
          return dfdz_out
docs: Evaluate the first derivative with respect to z 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.
          z : np.array
               Third input values; should be of same shape as x.
  
          Returns
          -------
          dfdz_out : np.array
              First derivative of function with respect to the third input,
              evaluated at (x,y,z), of same shape as inputs.