code: def config(client, key, value):
      
      if value is None:
          cfg = client.repo.config_reader()
          click.echo(cfg.get_value(*_split_section_and_key(key)))
      else:
          with client.repo.config_writer() as cfg:
              section, config_key = _split_section_and_key(key)
              cfg.set_value(section, config_key, value)
              click.echo(value)
docs: Get and set Renku repository and global options.