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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 file_checksum(fname):
 """Return md5 checksum of file. Note: only works for files < 4GB. Parameters filename : str File used to calculate checksum. Returns ------- checkum : str """

    size = os.path.getsize(fname)
    with open(fname, "r+") as f:
        checksum = hashlib.md5(mmap.mmap(f.fileno(), size)).hexdigest()
    return checksum