def METHOD_NAME(self):
    '''
    :returns: the member of the structure that is being accessed.
    :rtype: (sub-class of) :py:class:`psyclone.psyir.nodes.Member`
    :raises InternalError: if the first child of this node is not an \
                           instance of Member.
    '''
    if not isinstance(self.children[0], Member):
        raise InternalError(
            f"{type(self).__name__} malformed or incomplete. The first "
            f"child must be an instance of Member, but found "
            f"'{type(self.children[0]).__name__}'")
    return self.children[0]