code: def timeloop(t, t_stop, dt, dx, dy, u, um, k):
      while t <= t_stop:
          t += dt
          new_u = calculate_u(dt, dx, dy, u, um, k)
          um = u
          u = new_u
      return u
  
label_desc: Use image node_id 1 for calling a global function with example usage: timeloop(t, t_stop, dt, dx, dy, u, um, k) and returns: u