code: def null_concept(self):
          
          # 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)
docs: 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.