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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 null_concept(self):
 """Return the null concept of this subsystem. The null concept is a point in concept space identified with the unconstrained cause and effect repertoire of this subsystem. """

        # Unconstrained cause repertoire.
        cause_repertoire = self.cause_repertoire((), ())
        # Unconstrained effect repertoire.
        effect_repertoire = self.effect_repertoire((), ())

        # Null cause.
        cause = MaximallyIrreducibleCause(
            _null_ria(Direction.CAUSE, (), (), cause_repertoire))
        # Null effect.
        effect = MaximallyIrreducibleEffect(
            _null_ria(Direction.EFFECT, (), (), effect_repertoire))

        # All together now...
        return Concept(mechanism=(),
                       cause=cause,
                       effect=effect,
                       subsystem=self)