单词unmappable
网络: 无从标绘；不可标测
True. Some characters lack a best-fit representation; these characters are called unmappable.
一些字符缺少最合适的表示形式；这些字符称为无法映射的字符。
You can use the second parameter to control throwing an exception on unmappable characters.
可以使用第二个参数控制在遇到无法映射的字符时是否引发异常。