docs: function getCachedImageSizeFromUrl(url) {
      if (!url || url === undefined || url === null) {
          return;
      }
  
      // image size is not in cache
      if (!cache[url]) {
          return imageSize.getImageSizeFromUrl(url).then(function (res) {
              cache[url] = res;
  
              debug('Cached image:', url);
  
              return cache[url];
          }).catch(common.errors.NotFoundError, function () {
              debug('Cached image (not found):', url);
              // in case of error we just attach the url
              cache[url] = url;
  
              return cache[url];
          }).catch(function (err) {
              debug('Cached image (error):', url);
              common.logging.error(err);
  
              // in case of error we just attach the url
              cache[url] = url;
  
              return cache[url];
          });
      }
      debug('Read image from cache:', url);
      // returns image size from cache
      return cache[url];
  }