def sum(self, projection=None):
        if projection:
            return sum(self.map(projection))
        else:
            return sum(self)
Tests that a SaltCloudSystemExit is raised when trying to call list_nodes
dataset/ETHPy150Open EntilZha/PyFunctional/functional/pipeline.py/Sequence.sum--crossover with--dataset/ETHPy150Open saltstack/salt/tests/unit/cloud/clouds/dimensiondata_test.py/DimensionDataTestCase.test_list_nodes_call