<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def pre(self):
 """ Initialize system for power flow study Returns ------- None """

        logger.info('-> Power flow study: {} method, {} start'.format(
            self.config.method.upper(), 'flat' if self.config.flatstart else 'non-flat')
        )

        t, s = elapsed()

        system = self.system
        dae = self.system.dae

        system.dae.init_xy()

        for device, pflow, init0 in zip(system.devman.devices,
                                        system.call.pflow, system.call.init0):
            if pflow and init0:
                system.__dict__[device].init0(dae)

        # check for islands
        system.check_islands(show_info=True)

        t, s = elapsed(t)
        logger.debug('Power flow initialized in {:s}.'.format(s))