Small change to prevent a bug where generation mixes aren't created if replace_egrid is False and the selected aggregation region is BA, FERC, or US. For the BA and FERC regions, the reference eGrid data doesn't include BA or FERC names. The routine that uses reference eGrid data doesn't support US aggregation. The fix just re-directs to using the generation_df itself.
Small change to prevent a bug where generation mixes aren't created if replace_egrid is False and the selected aggregation region is BA, FERC, or US. For the BA and FERC regions, the reference eGrid data doesn't include BA or FERC names. The routine that uses reference eGrid data doesn't support US aggregation. The fix just re-directs to using the generation_df itself.