code: def convex_conj(self):
          
          conj_exp = conj_exponent(self.pointwise_norm.exponent)
          return GroupL1Norm(self.domain, exponent=conj_exp)
docs: Convex conjugate functional of IndicatorLpUnitBall.
  
          Returns
          -------
          convex_conj : GroupL1Norm
              The convex conjugate is the the group L1-norm.