def insert(self, index, item):
        """ Inserts the *item* before the *index* into the `Sequence`.

        :param int index: `Sequence` index.
        :param item: any :class:`Structure`, :class:`Sequence`, :class:`Array`
            or :class:`Field` instance.
        """
        if not is_any(item):
            raise MemberTypeError(self, item, member=len(self))
        self._data.insert(index, item)