Google Vision API possible memory leak

Question

I'm trying to make an app to process a set of frames, stored as jpg into the app using Google-vision API.

The pipeline is simple.

1) I create the detector with some options:

     _options = @{
                  GMVDetectorFaceLandmarkType : @(GMVDetectorFaceLandmarkAll),
                  GMVDetectorFaceClassificationType : @(GMVDetectorFaceClassificationAll),
                  GMVDetectorFaceTrackingEnabled : @(NO)
                  };
    _faceDetector = [GMVDetector detectorOfType:GMVDetectorTypeFace options:_options];

2) I read a frame with this method:

    UIImage *image = [UIImage imageWithContentsOfFile:imFile];

The path contained in imFile is correct, I can see the Image representation

3) At last, I process the frame:

NSArray<GMVFaceFeature *> *faces = [_faceDetector featuresInImage:image options:nil];

With this code I can process some frames, but when analyzing a lot of them, the memory usage of the app keeps increasing and the app is killed automatically.

I've tried to track the memory leak, but as far as I tracked it, it comes from inside the last part, inside the [detector featuresInImage...]

Is there something I am doing wrong, or is there a memory leak inside it? I have tried to find any issue from google but couldn't manage to find it.

EDIT:

Here is what I do with each of the results of the detector:

    if ([faces count]>0){
        GMVFaceFeature *face = [faces objectAtIndex:0];
        NSFileHandle *myHandle = [NSFileHandle fileHandleForWritingAtPath:filename];
        [myHandle seekToEndOfFile];

        NSString* lineToWrite = [NSString stringWithFormat:@"%u",fNumber];
        lineToWrite = [lineToWrite stringByAppendingString:[NSString stringWithFormat:@",%f",face.smilingProbability]];
        lineToWrite = [lineToWrite stringByAppendingString:@"\n"];
        NSError *errorWrite;
        [myHandle writeData:[lineToWrite dataUsingEncoding:NSUTF8StringEncoding]];

        if(errorWrite){
            NSLog(@"%@",errorWrite);
        }
    }

The method ends there. So basically what I do is creating a file and writing in it.