def set_unit_system_type(self, unit_system_type):
self._unit_system_type = unit_system_type<EOL>
Sets the unit system type.

        :param unit_system_type: the unit system type
        :type unit_system_type: ``osid.type.Type``
        :raise: ``NullArgument`` -- ``unit_system_type`` is ``null``

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