code: func PopoverNew(relative IWidget) (*Popover, error) {
  	//Takes relative to widget
  	var c *C.struct__GtkWidget
  	if relative == nil {
  		c = C.gtk_popover_new(nil)
  	} else {
  		c = C.gtk_popover_new(relative.toWidget())
  	}
  	if c == nil {
  		return nil, nilPtrErr
  	}
  	return wrapPopover(glib.Take(unsafe.Pointer(c))), nil
  }
docs: //gtk_popover_new()