A less-than filter chain.

        >>> request_time = EventExpression('request', 'elapsed_ms')
        >>> filtered = request_time.lt('elapsed_ms', 500)
        >>> print(filtered)
        request(elapsed_ms).lt(elapsed_ms, 500)

def lt(self, event_property, value):
        """A less-than filter chain.

        >>> request_time = EventExpression('request', 'elapsed_ms')
        >>> filtered = request_time.lt('elapsed_ms', 500)
        >>> print(filtered)
        request(elapsed_ms).lt(elapsed_ms, 500)
        """
        c = self.copy()
        c.filters.append(filters.LT(event_property, value))
        return c