@contextlib.contextmanager
    def _transaction(self):
        with self._memory_lock(write=True):
            yield
compute absolute distance between two variants
dataset/ETHPy150Open openstack/taskflow/taskflow/persistence/backends/impl_memory.py/Connection._transaction--crossover with--dataset/ETHPy150Open adamewing/bamsurgeon/scripts/evaluator.py/var_dist