def on_benchmark_start(self, phase=None):
        self.telemetry.on_benchmark_start(phase)
        for node in self.nodes:
            node.on_benchmark_start(phase)
Return a prefix based on options passed from command line
dataset/ETHPy150Open elastic/rally/esrally/cluster.py/Cluster.on_benchmark_start--crossover with--dataset/ETHPy150Open SpriteLink/NIPAP/nipap-cli/nipap_cli/nipap_cli.py/_prefix_from_opts