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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 variables(self) -> Set[str]: """A set of all different |Node.variable| values of the |Node| objects directly connected to the actual |Element| object. Suppose there is an element connected to five nodes, which (partly) represent different variables: Property |Element.variables| puts all the different variables of these nodes together: ['X', 'Y1', 'Y2', 'Y3', 'Y4'] """

        variables: Set[str] = set()
        for connection in self.__connections:
            variables.update(connection.variables)
        return variables