def check_visitors(cls):
for name in dir(cls):<EOL><INDENT>if name.startswith("<STR_LIT>"):<EOL><INDENT>if name[<NUM_LIT:6>:] not in CLASS_NAMES:<EOL><INDENT>raise Exception(u"<STR_LIT>".format(name))<EOL><DEDENT><DEDENT><DEDENT>return cls<EOL>
Check that a checker's visitors are correctly named.

    A checker has methods named visit_NODETYPE, but it's easy to mis-name
    a visit method, and it will never be called.  This decorator checks
    the class to see that all of its visitors are named after an existing
    node class.