code: func (v *Notebook) SetTabLabelText(child IWidget, tabText string) {
  	cstr := C.CString(tabText)
  	defer C.free(unsafe.Pointer(cstr))
  	C.gtk_notebook_set_tab_label_text(v.native(), child.toWidget(),
  		(*C.gchar)(cstr))
  }
docs: // SetTabLabelText() is a wrapper around gtk_notebook_set_tab_label_text().