def varimp(self, use_pandas=False):
        """
        Pretty print the variable importances, or return them in a list/pandas DataFrame.

        :param bool use_pandas: If True, then the variable importances will be returned as a pandas data frame.

        :returns: A dictionary of lists or Pandas DataFrame instances.
        """
        return {model.model_id: model.varimp(use_pandas) for model in self.models}