docs: def init_parser(cls, parser):
          """Initialize argument parser"""
          subparsers = parser.add_subparsers(title='Search domain')
  
          # Compound subcommand
          parser_compound = subparsers.add_parser(
              'compound', help='Search in compounds')
          parser_compound.set_defaults(which='compound')
          parser_compound.add_argument(
              '--id', '-i', dest='id', metavar='id',
              action=FilePrefixAppendAction, type=text_type, default=[],
              help='Compound ID')
          parser_compound.add_argument(
              '--name', '-n', dest='name', metavar='name',
              action=FilePrefixAppendAction, type=text_type, default=[],
              help='Name of compound')
  
          # Reaction subcommand
          parser_reaction = subparsers.add_parser(
              'reaction', help='Search in reactions')
          parser_reaction.set_defaults(which='reaction')
          parser_reaction.add_argument(
              '--id', '-i', dest='id', metavar='id',
              action=FilePrefixAppendAction, type=str, default=[],
              help='Reaction ID')
          parser_reaction.add_argument(
              '--compound', '-c', dest='compound', metavar='compound',
              action=FilePrefixAppendAction, type=str, default=[],
              help='Comma-separated list of compound IDs')