code: def add_pressure_diffusion(dU, U_hat, K2, K, P_hat, K_over_K2, nu):
      du0, du1, du2 = dU[0], dU[1], dU[2]
      k_0, k_1, k_2 = K_over_K2[0], K_over_K2[1], K_over_K2[2]
      P_hat[:] = du0 * k_0 + du1 * k_1 + du2 * k_2
      dU[:] = dU - P_hat * K - nu * K2 * U_hat
      return P_hat
  
label_desc: Use image node_id 3 for calling a global function with example usage: add_pressure_diffusion(dU, U_hat, K2, K, P_hat, K_over_K2, nu) and returns: P_hat