尝试语句语法

我一直在阅读python文档,有人可以帮我解释一下吗？

try_stmt  ::=  try1_stmt | try2_stmt
try1_stmt ::=  "try" ":" suite
               ("except" [expression [("as" | ",") identifier]] ":" suite)+
               ["else" ":" suite]
               ["finally" ":" suite]
try2_stmt ::=  "try" ":" suite
               "finally" ":" suite

我最初认为这意味着try语句必须具有任何格式

try和finally或

try,except,else和finally.

但在阅读文档后,它提到了这else是可选的,也是如此finally.所以,我想知道文档的目的是什么,向我们展示上面格式的代码？