code: func (v *CellLayout) AddAttribute(cell ICellRenderer, attribute string, column int) {
  	cstr := C.CString(attribute)
  	defer C.free(unsafe.Pointer(cstr))
  	C.gtk_cell_layout_add_attribute(v.native(), cell.toCellRenderer(),
  		(*C.gchar)(cstr), C.gint(column))
  }
docs: // AddAttribute() is a wrapper around gtk_cell_layout_add_attribute().