code: public void purge(String cacheKey) {
          try {
              if (useMemoryCache) {
                  if (memoryCache != null) {
                      memoryCache.remove(cacheKey);
                  }
              }
  
              if (useDiskCache) {
                  if (diskLruCache != null) {
                      diskLruCache.remove(cacheKey);
                  }
              }
          } catch (Exception e) {
              Log.w(TAG, "Could not remove entry in cache purge", e);
          }
      }
docs: Removes the value connected to the given key
  from all levels of the cache. Will not throw an
  exception on fail.
  
  @param cacheKey