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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 get_username(self):
 """ Gets the user name. The value can be stored in parameters "username" or "user". :return: the user name. """

        username = self.get_as_nullable_string("username")
        username = username if username != None else self.get_as_nullable_string("user")
        return username