code: def udd(self, i, k, l):
      g = self.g
      x = self.x
      r = 0
      for m in [0, 1, 2, 3]:
          r += (
              g.uu(i, m)
              / 2
              * (
                  g.dd(m, k).diff(x[l])
                  + g.dd(m, l).diff(x[k])
                  - g.dd(k, l).diff(x[m])
              )
          )
      return r
  
imports: from sympy import exp, Symbol, sin, dsolve, Function, Matrix, Eq, pprint, solve
label_desc: Use image node_id 2 for calling the G obj's underlying member method code with example usage: obj.udd(i, k, l) and returns: r