public static String unifyCollisionChars(String topic) {
        return topic.replace('.', '_');
    }
@Test
    public void testUnifyCollisionChars() {
        assertEquals("topic", Topic.unifyCollisionChars("topic"));
        assertEquals("_topic", Topic.unifyCollisionChars(".topic"));
        assertEquals("_topic", Topic.unifyCollisionChars("_topic"));
        assertEquals("__topic", Topic.unifyCollisionChars("_.topic"));
    }