    def _read_csv(self, csv_path):
        logger.info("Reading Dataframe from %s", csv_path)
        df = pd.read_csv(csv_path)
        if 'seqname' in df:
            # by default, Pandas will infer the type as int,
            # then switch to str when it hits non-numerical
            # chromosomes. Make sure whole column has the same type
            df['seqname'] = df['seqname'].map(str)
        return df