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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 leftsibling_in_level(self):
 """ Node to the left of the current node at the same level For example see :mod:`sqlalchemy_mptt.tests.cases.get_tree.test_leftsibling_in_level` """
  # noqa
        table = _get_tree_table(self.__mapper__)
        session = Session.object_session(self)
        current_lvl_nodes = session.query(table) \
            .filter_by(level=self.level).filter_by(tree_id=self.tree_id) \
            .filter(table.c.lft < self.left).order_by(table.c.lft).all()
        if current_lvl_nodes:
            return current_lvl_nodes[-1]
        return None