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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 remove_children(self, id_):
 """Removes all childrenfrom an ``Id``. arg: id (osid.id.Id):
 the ``Id`` of the node raise: NotFound - an node identified by the given ``Id`` was not found raise: NullArgument - ``id`` is ``null`` raise: OperationFailed - unable to complete request raise: PermissionDenied - authorization failure *compliance: mandatory -- This method must be implemented.* """

        results = self._rls.get_relationships_by_genus_type_for_source(id_, self._relationship_type)
        if results.available() == 0:
            raise errors.NotFound()
        for r in results:
            self._ras.delete_relationship(r.get_id())