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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 cube(f):
 """Read a full cube from a file Takes an open segy file (created with segyio.open) or a file name. If the file is a prestack file, the cube returned has the dimensions ``(fast, slow, offset, sample)``. If it is post-stack (only the one offset), the dimensions are normalised to ``(fast, slow, sample)`` Parameters f : str or segyio.SegyFile Returns ------- cube : numpy.ndarray Notes ----- .. versionadded:: 1.1 """


    if not isinstance(f, segyio.SegyFile):
        with segyio.open(f) as fl:
            return cube(fl)

    ilsort = f.sorting == segyio.TraceSortingFormat.INLINE_SORTING
    fast = f.ilines if ilsort else f.xlines
    slow = f.xlines if ilsort else f.ilines
    fast, slow, offs = len(fast), len(slow), len(f.offsets)
    smps = len(f.samples)
    dims = (fast, slow, smps) if offs == 1 else (fast, slow, offs, smps)
    return f.trace.raw[:].reshape(dims)