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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 url_unsplit (parts):
 """Rejoin URL parts to a string."""

    if parts[2] == default_ports.get(parts[0]):
        return "%s://%s%s" % (parts[0], parts[1], parts[3])
    return "%s://%s:%d%s" % parts