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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 secured_clipboard(item):
 """This clipboard only allows 1 paste """

    expire_clock = time.time()
    def set_text(clipboard, selectiondata, info, data):
        # expire after 15 secs
        if 15.0 >= time.time() - expire_clock:
            selectiondata.set_text(item.get_secret())
            clipboard.clear()
    def clear(clipboard, data):
        """Clearing of the buffer is deferred this only gets called if the 
        paste is actually triggered
        """
        pass
    targets = [("STRING", 0, 0)
              ,("TEXT", 0, 1)
              ,("COMPOUND_TEXT", 0, 2)
              ,("UTF8_STRING", 0, 3)]
    cp = gtk.clipboard_get()
    cp.set_with_data(targets, set_text, clear)