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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 list_signals(self):
 """ Prints a list of all registered signals. Including description and plugin name. """

        print("Signal list")
        print("***********\n")
        for key, signal in self.app.signals.signals.items():
            print("%s (%s)\n  %s\n" % (signal.name, signal.plugin.name, signal.description))