def getUnder(self):
        if self.unders:
            return self.unders[0]
        else:
            None
Harness to test if the FrameSet.__and__ call works properly.
dataset/ETHPy150Open ioflo/ioflo/ioflo/base/framing.py/Frame.getUnder--crossover with--dataset/ETHPy150Open sqlboy/fileseq/test/run.py/TestFrameSet._check___and__