code: @CheckReturnValue
      public MessageAction clearFiles(BiConsumer<String, InputStream> finalizer)
      {
          Checks.notNull(finalizer, "Finalizer");
          for (Iterator<Map.Entry<String, InputStream>> it = files.entrySet().iterator(); it.hasNext();)
          {
              Map.Entry<String, InputStream> entry = it.next();
              finalizer.accept(entry.getKey(), entry.getValue());
              it.remove();
          }
          clearResources();
          return this;
      }
docs: Clears all previously added files
  
  @param  finalizer
  BiConsumer useful to <b>close</b> remaining resources,
  the consumer will receive the name as a string parameter and the resource as {@code InputStream}.
  
  @return Updated MessageAction for chaining convenience
  
  @see    java.io.Closeable