It is trying to tell you that there is no point in using a lambda at all.
Instead of writing your code like this:
results = " ".join(rdd.map(lambda x: save_and_show(x)).collect())
You should write it like this:
results = " ".join(rdd.map(save_and_show.collect())
It just assumes that all the values that are in the rdd will be the same as all the values in the function.