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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 _readable_part_size(num_bytes):
    "Returns the file size in readable form."
    B = num_bytes
    KB = float(1024)
    MB = float(KB * 1024)
    GB = float(MB * 1024)
    TB = float(GB * 1024)

    if B < KB:
        return '{0} {1}'.format(B, 'bytes' if B != 1 else 'byte')
    elif KB <= B < MB:
        return '{0:.2f} KiB'.format(B/KB)
    elif MB <= B < GB:
        return '{0:.2f} MiB'.format(B/MB)
    elif GB <= B < TB:
        return '{0:.2f} GiB'.format(B/GB)
    elif TB <= B:
        return '{0:.2f} TiB'.format(B/TB)