def max_stop(self):
m = <NUM_LIT:0><EOL>for r in self:<EOL><INDENT>if r.is_open():<EOL><INDENT>return None<EOL><DEDENT>m = max(m, r.stop)<EOL><DEDENT>return m<EOL>
:returns: maximum stop in list or None if there's at least one open range
:type: int, float or None