@abc.abstractmethod<EOL><INDENT>def convert_unit(self, source_unit, source_unit_type, target_unit_type):<DEDENT>
return<EOL>
Convert a unit of measurement.

        :param source_unit: the measure to convert
        :type source_unit: ``decimal``
        :param source_unit_type: the type of measure specified
        :type source_unit_type: ``osid.type.Type``
        :param target_unit_type: the type of converted measure
        :type target_unit_type: ``osid.type.Type``
        :return: resulting measure
        :rtype: ``decimal``
        :raise: ``NullArgument`` -- ``null`` argument provided
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure
        :raise: ``Unsupported`` -- ``LocaleManager.supportsUnitTypesForConversion(measureType, conversionType)`` is false

        *compliance: mandatory -- This method must be implemented.*