Custom render functions for "optgroup_header" / "optgroup" should also pass $optgroup element in data parameter

[picov]

I'm referring to current 2.4.3 version.
Custom render functions for "optgroup_header" / "optgroup" should also pass $optgroup element in data parameter (in the same way of the "option" and "item" render functions that pass data.$option element).
This could be very usefull for custom styling/icons ecc based on optgroup CSS classes and not on optgroup index/value.

Ex.:
In the select element below I can read "top-position" and "top-destination" classes from the "option" render function using the data.$option parameter, but it seems that there is no way to read SEARCH_D and SEARCH_P classes inside "optgroup_header" and "optgroup" functions.

<select id="search_terms_picker" name="search_terms[]" multiple="multiple"  data-placeholder="filters">
	<optgroup label="DESTINATIONS" class="SEARCH_D">
		<option  value="destination_id_7" >Tuscany</option>
		<option  value="destination_id_2" class="top-destination">Sardinia</option>
		<option  value="destination_id_3">Sicily</option>
		....			
	</optgroup>
	<optgroup label="POSITIONS" class="SEARCH_P">
		<option value="position_id_0" class="">inland</option>
		<option value="position_id_1" class="top-position">coastal</option>
	</optgroup>
...