def __new__(cls):
        if connection.vendor == "postgresql":
            version = get_postgresql_version(connection)
            if version > 80400:
                return PostgresSearchBackend()
            if version > 80300:
                return PostgresLegacySearchBackend()
        if connection.vendor == "mysql":
            return MySQLSearchBackend()
        return RegexSearchBackend()
Append the vcf_header from a chunk_db
dataset/ETHPy150Open etianen/django-watson/src/watson/backends.py/AdaptiveSearchBackend.__new__--crossover with--dataset/ETHPy150Open arq5x/gemini/gemini/gemini_merge_chunks.py/append_vcf_header