code: public static void releaseBuffer(Object message, RequestContext ctx) {
          final IdentityHashMap<Object, ByteBuf> buffers = ctx.attr(BUFFERS).get();
          checkState(buffers != null,
                     "Releasing buffer even though storeBuffer has not been called.");
          final ByteBuf removed = buffers.remove(message);
          if (removed == null) {
              throw new IllegalArgumentException("The provided message does not have a stored buffer.");
          }
          removed.release();
      }
docs: Releases the {@link ByteBuf} backing the provided {@link Message}.