def update_command(self, command, args=None):
if command is None:<EOL><INDENT>self._command = lambda: None<EOL><DEDENT>else:<EOL><INDENT>if args is None:<EOL><INDENT>self._command = command<EOL><DEDENT>else:<EOL><INDENT>self._command = utils.with_args(command, *args)<EOL><DEDENT><DEDENT>
Updates the callback command which is called when the ButtonGroup
changes.

Setting to `None` stops the callback.

:param callback command:
    The callback function to call.

:param callback args:
    A list of arguments to pass to the widgets `command`, defaults to
    `None`.