def _iter_groups(self, data):
        """
        Iterate over the groups in `data` after grouping by
        `segmentation_col`. Skips any groups for which there
        is no model stored.

        Yields tuples of (name, df) where name is the group key
        and df is the group DataFrame.

        Parameters
        ----------
        data : pandas.DataFrame
            Must have a column with the same name as `segmentation_col`.

        """
        groups = data.groupby(self.segmentation_col)

        for name in self.models:
            yield name, groups.get_group(name)
Iterate over the groups in `data` after grouping by
        `segmentation_col`. Skips any groups for which there
        is no model stored.

        Yields tuples of (name, df) where name is the group key
        and df is the group DataFrame.

        Parameters
        ----------
        data : pandas.DataFrame
            Must have a column with the same name as `segmentation_col`.