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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 imsave(filename, im, format=None):
 """Save image data to disk Requires imageio or PIL. Parameters filename : str Filename to write. im : array Image data. format : str | None Format of the file. If None, it will be inferred from the filename. See also -------- imread, read_png, write_png """

    # Import imageio or PIL
    imageio, PIL = _check_img_lib()
    if imageio is not None:
        return imageio.imsave(filename, im, format)
    elif PIL is not None:
        pim = PIL.Image.fromarray(im)
        pim.save(filename, format)
    else:
        raise RuntimeError("imsave requires the imageio or PIL package.")