context: A middle-aged man works under the engine of a train on rail tracks.
hypothesis: We believe that a man is doing work on a black Amtrack train.
valid_hypothesis: There is almost no chance that a man is doing work on a black Amtrack train.
invalid_hypothesis: We believe that a man is doing work on a black Amtrack train.
hypothesis_assertion: A man is doing work on a black Amtrack train.