'The names and values of options in a group.
Useful for copying options into Application settings::
from tornado.options import define, parse_command_line, options
define(\'template_path\', group=\'application\')
define(\'static_path\', group=\'application\')
parse_command_line()
application = Application(
handlers, **options.group_dict(\'application\'))
.. versionadded:: 3.1'

def group_dict(self, group):

    return dict(((name, opt.value()) for (name, opt) in self._options.items() if ((not group) or (group == opt.group_name))))
