Return a pandas DataFrame for each model and dataset.

        Parameters
        ----------
        recommended_only : bool, optional
            If True, only recommended models for each session are included. If
            no model is recommended, then a row with it's ID will be included,
            but all fields will be null.
        include_io :  bool, optional
            If True, then the input/output files from BMDS will also be
            included, specifically the (d) input file and the out file.

        Returns
        -------
        out : pandas.DataFrame
            Data frame containing models and outputs

def to_df(self, recommended_only=False, include_io=True):
        """
        Return a pandas DataFrame for each model and dataset.

        Parameters
        ----------
        recommended_only : bool, optional
            If True, only recommended models for each session are included. If
            no model is recommended, then a row with it's ID will be included,
            but all fields will be null.
        include_io :  bool, optional
            If True, then the input/output files from BMDS will also be
            included, specifically the (d) input file and the out file.

        Returns
        -------
        out : pandas.DataFrame
            Data frame containing models and outputs

        """
        od = BMDS._df_ordered_dict(include_io)
        [
            session._add_to_to_ordered_dict(od, i, recommended_only)
            for i, session in enumerate(self)
        ]
        return pd.DataFrame(od)