def _add_minimization_vars(self):
self._z = self._prob.namespace(self._model.reactions, lower=<NUM_LIT:0>)<EOL>v = self._v.set(self._model.reactions)<EOL>z = self._z.set(self._model.reactions)<EOL>self._prob.add_linear_constraints(z >= v, v >= -z)<EOL>
Add variables and constraints for L1 norm minimization.