code: def diffusePurePython(u, tempU, iterNum):
      """
      Apply nested iteration for the Forward-Euler Approximation
      """
      mu = 0.1
      row = u.shape[0]
      col = u.shape[1]
  
      for n in range(iterNum):
          for i in range(1, row - 1):
              for j in range(1, col - 1):
                  tempU[i, j] = u[i, j] + mu * (
                      u[i + 1, j]
                      - 2 * u[i, j]
                      + u[i - 1, j]
                      + u[i, j + 1]
                      - 2 * u[i, j]
                      + u[i, j - 1]
                  )
          for i in range(1, row - 1):
              for j in range(1, col - 1):
                  u[i, j] = tempU[i, j]
                  tempU[i, j] = 0.0
  
label_desc: Use image node_id 1 for calling a global function with example usage: diffusePurePython(u, tempU, iterNum) without return types