Select menu with gwcode_categories

gw_categories select-menu

[select name="category[]" id="categories" multiple="multiple"]
{exp:gwcode_categories channel="locations_channel" style="linear"}
    {if "{new_group}"=="yes"}
      {if {cat_count}>1}
        [/optgroup]
      {/if}
      [optgroup label="{cat_group_name}"]
    {/if}
    [option value="{cat_id}"]{cat_name}[/option]
{/exp:gwcode_categories}
[/optgroup]
[/select]

/* with end_group*/

	<pre>
	{exp:gwcode_categories channel="locations_channel" style="linear"}
	{if "{new_group}"=="yes"}[optgroup label="{cat_group_name}"]
	{/if}[option value="{cat_id}"]{cat_name}[/option]{if "{end_group}"=="yes"}

	[/optgroup]{/if}
	{/exp:gwcode_categories}
	</pre>