code: protected String generateIdentityKey() {
          if (mRequest.getImageReuseInfo() == null) {
              return getIdentityUrl();
          } else {
              return joinSizeTagToKey(getIdentityUrl(), mRequest.getImageReuseInfo().getIdentitySize());
          }
      }
docs: Generate the identity key.
  <p/>
  This key should be related to the unique image this task is requesting: the size, the remote url.
  
  @return