@abc.abstractmethod<EOL><INDENT>def get_distance_value(self):<DEDENT>
return<EOL>
Gets the value if it is a ``Distance``.

        :return: the value
        :rtype: ``osid.mapping.Distance``
        :raise: ``IllegalState`` -- ``Parameter.getSyntax() != DISTANCE``

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