code: @NotNull
  	public static ByteBuf append(@NotNull ByteBuf to, @NotNull ByteBuf from) {
  		assert !to.isRecycled() && !from.isRecycled();
  		if (to.readRemaining() == 0) {
  			to.recycle();
  			return from;
  		}
  		to = ensureWriteRemaining(to, from.readRemaining());
  		to.put(from);
  		from.recycle();
  		return to;
  	}
docs: Appends one ByteBuf to another ByteBuf. If target ByteBuf
  can't accommodate the ByteBuf to be appended, a new ByteBuf
  is created which contains both target and source ByteBufs data.
  The source ByteBuf is recycled after append.
  <p>
  If target ByteBuf has no readable bytes, it is being recycled
  and the source ByteBuf is returned.
  <p>
  Both ByteBufs must be not recycled before the operation.
  
  @param to the target ByteBuf to which another ByteBuf will be appended
  @param from the source ByteBuf to be appended
  @return ByteBuf which contains the result of the appending