code: private static String getCacheKey(String url, int maxWidth, int maxHeight, ScaleType scaleType) {
          return "#W" + maxWidth + "#H" + maxHeight + "#S" + scaleType.ordinal() + url;
      }
docs: Creates a cache key for use with the L1 cache.
  @param url The URL of the request.
  @param maxWidth The max-width of the output.
  @param maxHeight The max-height of the output.
  @param scaleType The scaleType of the imageView.