atom | atom in a python example?

[jirislaby]

Hi, what's the purpose of atom being specified twice in here:

antlr4/doc/python-target.md

Line 16 in 811b7fd

expr : atom | ('+' | '-') expr | expr '**' expr | expr ('*' | '/') expr | expr ('+' | '-') expr | '(' expr ')' | atom ;

?

[kaby76]

It is a mistake. Correct it, but make sure the example works.