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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_available_sensors(cls, types=None):
 """ Return all available sensors. :param list types: the type of the sensor to look for. If types is None it will search for all available types. :returns: a list of sensor instances. :rtype: list """

        if not types:
            types = cls.TYPE_NAMES.keys()
        is_sensor = lambda s: any(s.startswith(hex(x)[2:]) for x in types)  # noqa
        return [
            cls(cls.RESOLVE_TYPE_STR[s[:2]], s[3:])
            for s in os.listdir(cls.BASE_DIRECTORY)
            if is_sensor(s)
        ]