def contains(self, event_property, value):
c = self.copy()<EOL>c.filters.append(filters.RE(event_property, "<STR_LIT>".format(<EOL>value=value)))<EOL>return c<EOL>
A string-contains filter chain.

        >>> request_time = EventExpression('request', 'elapsed_ms')
        >>> filtered = request_time.contains('path', 'event')
        >>> print(filtered)
        request(elapsed_ms).re(path, ".*event.*")