class_docstr: Mean absolute percentage error.
  
  Examples
  --------
  
  >>> from river import metrics
  
  >>> y_true = [3, -0.5, 2, 7]
  >>> y_pred = [2.5, 0.0, 2, 8]
  
  >>> metric = metrics.MAPE()
  >>> for yt, yp in zip(y_true, y_pred):
  ...     metric.update(yt, yp)
  
  >>> metric
  MAPE: 32.738095
code: def _eval(self, y_true, y_pred):
      if y_true == 0:
          return 0.0
      return abs(y_true - y_pred) / abs(y_true)
  
imports: from __future__ import annotations
  from river import metrics
label_desc: Use image node_id 1 for calling the MAPE obj's underlying member method code with example usage: obj._eval(y_true, y_pred) and returns: unknown, int