Added a test for getting labels from iOS image segmenter

mediapipe/tasks/ios/test/vision/image_segmenter/MPPImageSegmenterTests.mm

@@ -507,6 +507,22 @@ double softIOU(const float *mask1, const float *mask2, size_t size) {
   }];
 }
 
+#pragma mark GetLabelsTest
+
+- (void)testGetLabelsSucceeds {
+  MPPImageSegmenterOptions *options =
+      [self imageSegmenterOptionsWithModelFileInfo:kImageSegmenterModelFileInfo];
+
+  MPPImageSegmenter *imageSegmenter = [self createImageSegmenterWithOptionsSucceeds:options];
+  
+  NSArray *expectedLabels = @[@"background", @"aeroplane", @"bicycle", 
+  @"bird", @"boat", @"bottle", @"bus", @"car",@"cat", 
+  @"chair", @"cow", @"dining table", @"dog", @"horse", @"motorbike",
+  @"person", @"potted plant", @"sheep", @"sofa", @"train", @"tv"];
+
+  XCTAssertEqualObjects(imageSegmenter.labels, expectedLabels);
+}
+
 #pragma mark - Image Segmenter Initializers
 
 - (MPPImageSegmenterOptions *)imageSegmenterOptionsWithModelFileInfo:(MPPFileInfo *)fileInfo {