service_request = service.images().annotate(body={'requests': [{'image': {
    'content': image_content}, 'features': [{'type': 'LABEL_DETECTION',
    'maxResults': 1}]}]})
response = service_request.execute()
label = response['responses'][0]['labelAnnotations'][0]['description']
How do I call the Google Vision API with an image stored in Google Cloud Storage?