function open(type: GLib.VariantType): void {
    // Gjs wrapper for g_variant_builder_open()

Opens a subcontainer inside the given builder. When done adding items to the subcontainer, GLib.VariantBuilder.prototype.close must be called.

It is an error to call this function in any way that would cause an inconsistent value to be constructed (ie: adding too many values or a value of an incorrect type).

Since 2.24