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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 units(self):
 """ Get the units for every model in the scene, and raise a ValueError if there are mixed units. Returns units : str Units for every model in the scene """

        existing = [i.units for i in self.geometry.values()]

        if any(existing[0] != e for e in existing):
            # if all of our geometry doesn't have the same units already
            # this function will only do some hot nonsense
            raise ValueError('models in scene have inconsistent units!')

        return existing[0]