code: protected static CannotParseException missingXmlElements(ICalDataType... dataTypes) {
  		String[] elements = new String[dataTypes.length];
  		for (int i = 0; i < dataTypes.length; i++) {
  			ICalDataType dataType = dataTypes[i];
  			elements[i] = (dataType == null) ? "unknown" : dataType.getName().toLowerCase();
  		}
  		return missingXmlElements(elements);
  	}
docs: Creates a {@link CannotParseException}, indicating that the XML elements
  that the parser expected to find are missing from the property's XML
  element.
  @param dataTypes the expected data types (null for "unknown")
  @return the exception