Reloads configuration settings from a configuration file for the root package of the requested package/module.

This overwrites any changes that may have been made in ConfigItem objects. This applies for any items that are based on this file, which is determined by the root package of packageormod (e.g. 'astropy.cfg' for the 'astropy.config.configuration' module).

packageormod : str or None

The package or module name - see get_config for details.