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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 User(self, Username=''):
 """Queries a user object. :Parameters: Username : str Skypename of the user. :return: A user object. :rtype: `user.User` """

        if not Username:
            Username = self.CurrentUserHandle
        o = User(self, Username)
        o.OnlineStatus # Test if such a user exists.
        return o