<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _find_ble_controllers(self):
 """Get a list of the available and powered BLE controllers"""

        controllers = self.bable.list_controllers()
        return [ctrl for ctrl in controllers if ctrl.powered and ctrl.low_energy]