code: def smape(y, yhat):
      """Return the symmetric mean absolute percentage error.
  
      Args:
        y: An array containing the true values.
        yhat: An array containing the predicted values.
  
      Returns:
        The scalar SMAPE.
      """
      # https://en.wikipedia.org/wiki/Symmetric_mean_absolute_percentage_error
      assert len(yhat) == len(y)
      h = len(y)
      errors = np.abs(y - yhat) / (np.abs(y) + np.abs(yhat)) * 100
      return 2 / h * np.sum(errors)
  
imports: import numpy
label_desc: Use image node_id 1 for calling a global function with example usage: smape(y, yhat) and returns: unknown