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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 from_pickle(cls, filename):
 """Loads and Returns a Camera from a pickle file, given a filename."""

        with open(filename, 'rb') as f:
            cam = pickle.load(f)

        projection = cam.projection.copy()
        return cls(projection=projection, position=cam.position.xyz, rotation=cam.rotation.__class__(*cam.rotation[:]))