code: protected TLVElement readOnce(TLVElement element) throws TLVParserException {
          int tlvElementType = element.getType();
          if (!processedElements.contains(tlvElementType)) {
              processedElements.add(tlvElementType);
              return element;
          }
          throw new TLVParserException("Multiple TLV 0x" + Integer.toHexString(tlvElementType) + " elements. Only one is allowed.");
      }
docs: @param element
  TLV element of type to read only once.
  
  @return Instance of {@link TLVElement}.
  
  @throws TLVParserException
  when TLV element of given type is already processed.