docs: def accuracy_score(y, y_pred):
      """Calculates the fraction of the correctly
      classified samples over all.
      
      Parameters:
      -----------
      y : vector, shape (n_samples,)
      The target labels.
  
      y_pred : vector, shape (n_samples,)
      The predicted labels.
      
      Returns:
      --------
      accuracy : float number, the fraction
      of the correctly classified samples over all
      
      """
  
      y, y_pred = convert_assert(y, y_pred)
      return np.count_nonzero(y == y_pred) / y.size