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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 xray(im, direction='X'):
 r""" Simulates an X-ray radiograph looking through the porouls material in the specfied direction. The resulting image is colored according to the amount of attenuation an X-ray would experience, so regions with more solid will appear darker. Parameters im : array_like ND-image of the porous material with the solid phase marked as 1 or True direction : string Specify the axis along which the camera will point. Options are 'X', 'Y', and 'Z'. Returns ------- image : 2D-array A 2D greyscale image suitable for use in matplotlib\'s ```imshow``` function. """

    im = sp.array(~im, dtype=int)
    if direction in ['Y', 'y']:
        im = sp.transpose(im, axes=[1, 0, 2])
    if direction in ['Z', 'z']:
        im = sp.transpose(im, axes=[2, 1, 0])
    im = sp.sum(im, axis=0)
    return im