Gets the current evaluation result.

        Returns
        -------
        names : list of str
           Name of the metrics.
        values : list of float
           Value of the evaluations.

def get(self):
        """Gets the current evaluation result.

        Returns
        -------
        names : list of str
           Name of the metrics.
        values : list of float
           Value of the evaluations.
        """
        if self.num_inst == 0:
            return (self.name, float('nan'))
        else:
            return (self.name, self.sum_metric / self.num_inst)