@Test
public void testGetValueAsString() {

	MultipartBody multipartBody = MultipartBody.of(
		Collections.emptyMap(), __ -> _objectMapper,
		Collections.singletonMap("key", "value"));
	assertThat(multipartBody.getValueAsString("key"), is("value"));
	assertThat(multipartBody.getValueAsString("null"), is(nullValue()));
}