docs: def bulk_insert_extras(dialect_name: str,
                         fileobj: TextIO,
                         start: bool) -> None:
      """
      Writes bulk ``INSERT`` preamble (start=True) or end (start=False).
  
      For MySQL, this temporarily switches off autocommit behaviour and index/FK
      checks, for speed, then re-enables them at the end and commits.
  
      Args:
          dialect_name: SQLAlchemy dialect name (see :class:`SqlaDialectName`)
          fileobj: file-like object to write to
          start: if ``True``, write preamble; if ``False``, write end
      """
      lines = []
      if dialect_name == SqlaDialectName.MYSQL:
          if start:
              lines = [
                  "SET autocommit=0;",
                  "SET unique_checks=0;",
                  "SET foreign_key_checks=0;",
              ]
          else:
              lines = [
                  "SET foreign_key_checks=1;",
                  "SET unique_checks=1;",
                  "COMMIT;",
              ]
      writelines_nl(fileobj, lines)