<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def convex_conj(self):
 """The convex conjugate functional of the group L1-norm."""

        conj_exp = conj_exponent(self.pointwise_norm.exponent)
        return IndicatorGroupL1UnitBall(self.domain, exponent=conj_exp)