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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_descendants(self, include_self=False, depth=None):
 """Return all the descendants of this object."""

        params = {"%s__parent" % self._closure_childref():self.pk}
        if depth is not None:
            params["%s__depth__lte" % self._closure_childref()] = depth
        descendants = self._toplevel().objects.filter(**params)
        if not include_self:
            descendants = descendants.exclude(pk=self.pk)
        return descendants.order_by("%s__depth" % self._closure_childref())