@cached_property
    def blocks(self):
        return self._blocks
test the contract of load/refresh such that history is reset.
dataset/ETHPy150Open OP2/PyOP2/pyop2/petsc_base.py/Mat.blocks--crossover with--dataset/ETHPy150Open zzzeek/sqlalchemy/test/orm/test_events.py/RefreshTest.test_changes_reset