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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 denorm(self,arr):
 """Reverse the normalization done to a batch of images. Arguments: arr: of shape/size (N,3,sz,sz) """

        if type(arr) is not np.ndarray: arr = to_np(arr)
        if len(arr.shape)==3: arr = arr[None]
        return self.transform.denorm(np.rollaxis(arr,1,4))