code: public static ITag getNotNull(final byte[] tagBytes) {
  		ITag tag = find(tagBytes);
  		if (tag == null) {
  			tag = createUnknownTag(tagBytes);
  		}
  		return tag;
  	}
docs: If the tag is not found, this method returns the "[UNHANDLED TAG]" containing 'tagBytes'
  
  @param tagBytes
  @return