def METHOD_NAME(self, node):
    """
    Visits a single unit type element, checks for correct usage of units and builds the corresponding combined
    unit.
    :param node: a single unit type meta_model.
    :type node: ASTUnitType
    :return: a new type symbol representing this unit type.
    :rtype: type_symbol
    """
    if node.is_simple_unit():
        type_s = PredefinedTypes.get_type(node.unit)
        if type_s is None:
            code, message = Messages.unknown_type(str(node.unit))
            Logger.log_message(None, code, message, node.get_source_position(), LoggingLevel.ERROR)
            return
        node.set_type_symbol(type_s)
        self.symbol = type_s