def get_children(self, usage_id_filter=None):
        """
        Return instantiated XBlocks for each of this blocks ``children``.
        """
        if not self.has_children:
            return []

        return [
            self.get_child(usage_id)
            for usage_id in self.children
            if usage_id_filter is None or usage_id_filter(usage_id)
        ]
Return instantiated XBlocks for each of this blocks ``children``.