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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 getProtocolClasses(superclass=message.Message):
 """ Returns all the protocol classes that are subclasses of the specified superclass. Only 'leaf' classes are returned, corresponding directly to the classes defined in the protocol. """

    # We keep a manual list of the superclasses that we define here
    # so we can filter them out when we're getting the protocol
    # classes.
    superclasses = set([message.Message])
    thisModule = sys.modules[__name__]
    subclasses = []
    for name, class_ in inspect.getmembers(thisModule):
        if ((inspect.isclass(class_) and
                issubclass(class_, superclass) and
                class_ not in superclasses)):
            subclasses.append(class_)
    return subclasses