@Override
  public String getUriString() {
    return mKey;
  }
{@link CacheKey} implementation that is a simple wrapper around a {@link String} object.

<p>Users of CacheKey should construct it by providing a unique string that unambiguously
identifies the cached resource.
imagepipeline-base/src/main/java/com/facebook/cache/common/SimpleCacheKey.java