code: def start(self):
          
          assert not self.is_running(), 'Attempted to start an energy measurement while one was already running.'
  
          self._measurement_process = subprocess.Popen(
              [self._executable, '-r'],
              stdout=subprocess.PIPE,
              stderr=subprocess.PIPE,
              bufsize=10000,
              preexec_fn=os.setpgrp, # Prevent delivery of Ctrl+C to subprocess
              )
docs: Starts the external measurement program.