def get_base_types(self, type_=None):
raise Unimplemented()<EOL>
Gets the immediate base types of this type.

        arg:    type (osid.type.Type): a type
        return: (osid.type.TypeList) - the base types
        raise:  NullArgument - type is null
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        compliance: mandatory - This method must be implemented.