new_contents: DJMERCADOPAGO_CLIENT_ID = 'your-mp-client-id'
  DJMERCADOPAGO_CLIENTE_SECRET = 'your-mp-secret'
  DJMERCADOPAGO_SANDBOX_MODE = True
  DJMERCADOPAGO_CHECKOUT_PREFERENCE_BUILDER = \
      'full.path.to.checkout.builder.implementation.function'
  
subject: Update sample settings