docs: def add_database_args(parser):
      '''
      Add a standard set of database arguments for argparse
      '''
      parser.add_argument(
          'url',
          nargs='?',
          default='sqlite:///ncbi_taxonomy.db',
          type=sqlite_default(),
          help=('Database string URI or filename.  If no database scheme '
                'specified \"sqlite:///\" will be prepended. [%(default)s]'))
      db_parser = parser.add_argument_group(title='database options')
  
      # TODO: better description of what --schema does
      db_parser.add_argument(
          '--schema',
          help=('Name of SQL schema in database to query '
                '(if database flavor supports this).'))
  
      return parser