cfgvalue(section_id, set_value) {
		if (section_id == null)
			L.error('TypeError', 'Section ID required');

		if (arguments.length == 2) {
			this.data ??= {};
			this.data[section_id] = set_value;
		}

		return this.data?.[section_id];
	}
Query the underlying configuration value.

The default implementation of this method returns the cached return
value of [load()]{@link LuCI.form.AbstractValue#load}. It may be
overridden by user code to obtain the configuration value in a
different way.

@param {string} section_id
The configuration section ID

@throws {TypeError}
Throws a `TypeError` exception when no `section_id` was specified.

@returns {*}
Returns the configuration value.