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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 _init_redis(redis_spec):
 """ Return a StrictRedis instance or None based on redis_spec. redis_spec may be None, a Redis URL, or a StrictRedis instance """

        if not redis_spec:
            return
        if isinstance(redis_spec, six.string_types):
            return redis.StrictRedis.from_url(redis_spec)
        # assume any other value is a valid instance
        return redis_spec