code: public void setMatchETagNone(String etag) throws InvalidArgumentException {
      if (etag == null) {
        throw new InvalidArgumentException("ETag cannot be empty");
      }
      copyConditions.put("x-amz-copy-source-if-none-match", etag);
    }
docs: Set matching ETag none condition, copy object which does not
  match the following ETag.
  
  @throws InvalidArgumentException
  When etag is null