write(section_id, formvalue) {
		return this.map.data.set(
			this.uciconfig ?? this.section.uciconfig ?? this.map.config,
			this.ucisection ?? section_id,
			this.ucioption ?? this.option,
			formvalue);
	}
Write the current input value into the configuration.

This function is invoked upon saving the parent form when the option
element is valid and when its input value has been changed compared to
the initial value returned by
[cfgvalue()]{@link LuCI.form.AbstractValue#cfgvalue}.

The default implementation simply sets the given input value in the
UCI configuration (or the associated JavaScript object property in
case of `JSONMap` forms). It may be overridden by user code to
implement alternative save logic, e.g. to transform the input value
before it is written.

@param {string} section_id
The configuration section ID

@param {string|string[]}	formvalue
The input value to write.