code: func isVariadic(f *ast.FuncType) bool {
  	nargs := len(f.Params.List)
  	if nargs == 0 {
  		return false
  	}
  	_, ok := f.Params.List[nargs-1].Type.(*ast.Ellipsis)
  	return ok
  }
docs: // isVariadic returns whether the function is variadic.