code: public void registerParameterDataType(String parameterName, ICalDataType dataType) {
  		parameterName = parameterName.toLowerCase();
  		if (dataType == null) {
  			parameterDataTypes.remove(parameterName);
  		} else {
  			parameterDataTypes.put(parameterName, dataType);
  		}
  	}
docs: Registers the data type of an experimental parameter. Experimental
  parameters use the "unknown" data type by default.
  @param parameterName the parameter name (e.g. "x-foo")
  @param dataType the data type or null to remove