<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _config_stress(self):
 """ Configures the possible stress processes and modes """

        # Configure stress_process
        self.stress_exe = None
        stress_installed = False
        self.stress_exe = which('stress')
        if self.stress_exe:
            stress_installed = True
        else:
            self.stress_exe = which('stress-ng')
            if self.stress_exe:
                stress_installed = True

        self.firestarter = None
        firestarter_installed = False
        if os.path.isfile('./FIRESTARTER/FIRESTARTER'):
            self.firestarter = os.path.join(os.getcwd(),
                                            'FIRESTARTER', 'FIRESTARTER')
            firestarter_installed = True
        else:
            firestarter_exe = which('FIRESTARTER')
            if firestarter_exe is not None:
                self.firestarter = firestarter_exe
                firestarter_installed = True

        return StressController(stress_installed, firestarter_installed)