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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 elekta_xvi_fbp(ray_transform, padding=False, filter_type='Hann', frequency_scaling=0.6):
 """Approximation of the FDK reconstruction used in the Elekta XVI. Parameters ray_transform : `RayTransform` The ray transform to be used, should have an Elekta XVI geometry. padding : bool, optional Whether the FBP filter should use padding, increases memory use significantly. filter_type : str, optional Type of filter to apply in the FBP filter. frequency_scaling : float, optional Frequency scaling for FBP filter. Returns ------- elekta_xvi_fbp : `DiscreteLp` Examples -------- Create default FBP for default geometry: """

    fbp_op = odl.tomo.fbp_op(ray_transform,
                             padding=padding,
                             filter_type=filter_type,
                             frequency_scaling=frequency_scaling)

    return fbp_op