def add_flow_exception(exc):
global _flow_exceptions<EOL>if not isinstance(exc, type) or not issubclass(exc, Exception):<EOL><INDENT>raise TypeError('<STR_LIT>' % (exc,))<EOL><DEDENT>as_set = set(_flow_exceptions)<EOL>as_set.add(exc)<EOL>_flow_exceptions = tuple(as_set)<EOL>
Add an exception that should not be logged.

    The argument must be a subclass of Exception.