public Map<String, Object> getFields() {
        return ImmutableMap.copyOf(fields);
    }
@Test
    public void testGetFields() throws Exception {
        final Map<String, Object> fields = message.getFields();

        assertEquals(message.getId(), fields.get("_id"));
        assertEquals(message.getMessage(), fields.get("message"));
        assertEquals(message.getSource(), fields.get("source"));
        assertEquals(message.getField("timestamp"), fields.get("timestamp"));
    }