def METHOD_NAME(self, partition: EpaCemsPartition) -> pd.DataFrame:
    """Constructs dataframe from a zipfile for a given (year, state) partition."""
    archive = self.datastore.get_zipfile_resource(
        "epacems", **partition.get_filters()
    )
    # Get names of files in zip file
    files = self.datastore.get_zipfile_file_names(archive)
    # If archive has one csv file in it, this is a yearly CSV (archived after 08/23)
    # and this CSV does not need to be concatenated.
    if len(files) == 1 and files[0].endswith(".csv"):
        with archive.open(str(partition.get_annual_file()), "r") as csv_file:
            df = self._csv_to_dataframe(
                csv_file, ignore_cols=API_IGNORE_COLS, rename_dict=API_RENAME_DICT
            )
        return df
    else:
        raise AssertionError(f"Unexpected archive format. Found files: {files}.")