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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 sum_over_energy(self):
 """ Reduce a 3D counts cube to a 2D counts map """

        # Note that the array is using the opposite convention from WCS
        # so we sum over axis 0 in the array, but drop axis 2 in the WCS object
        return Map(np.sum(self.counts, axis=0), self.wcs.dropaxis(2))