def _register_expr(self, s):
        if not is_legal_name(s):
            expr = ExprEvaluator(s)
            if self._exprs is None:
                self._exprs = {}
            self._exprs[s] = expr
Returns the list of client counts per VM to use in staircase load.
dataset/ETHPy150Open OpenMDAO/OpenMDAO-Framework/openmdao.main/src/openmdao/main/case.py/Case._register_expr--crossover with--dataset/ETHPy150Open GoogleCloudPlatform/PerfKitBenchmarker/perfkitbenchmarker/linux_packages/ycsb.py/_GetThreadsPerLoaderList