public Request setExtras(Map<String, Object> extras) {
        this.extras.putAll(extras);
        return this;
    }
@Test
    public void testSetExtras() {
        Request request = new Request();
        Map<String, Object> extras = Collections.singletonMap("a", "1");
        request.setExtras(extras);
        request.putExtra("b", "2");
        assertThat(request.<String>getExtra("a")).isEqualTo("1");
        assertThat(request.<String>getExtra("b")).isEqualTo("2");
    }