code: def update(u):
      dx = 0.1
      dy = 0.1
      dx2 = dx * dx
      dy2 = dy * dy
      nx, ny = len(u), len(u[0])
      for i in range(1, nx - 1):
          for j in range(1, ny - 1):
              u[i][j] = (
                  (u[i + 1][j] + u[i - 1][j]) * dy2
                  + (u[i][j + 1] + u[i][j - 1]) * dx2
              ) / (2 * (dx2 + dy2))
  
label_desc: Use image node_id 1 for calling a global function with example usage: update(u) without return types