Sounds like another homework question. To provide any sort of meaningful graph, we need to know the part number of the transformer, its specs, and the frequency of the bipolar square wave.
However, in general, the principle here is that transformers do NOT pass DC. Since a bipolar square wave can be viewed as two DC values that are equal , opposite and alternate in time. The only thing that can pass through the transformer is the transitions or edges of the square wave. Therefore, the output is a series of impulse functions with alternating sign.