code: def _combine_costs(self, Npwl, Hpwl, Cpwl, fparm_pwl, any_pwl,
                         Npol, Hpol, Cpol, fparm_pol, npol, nw):
          
          NN = vstack([n for n in [Npwl, Npol] if n is not None], "csr")
  
          if (Hpwl is not None) and (Hpol is not None):
              Hpwl = hstack([Hpwl, csr_matrix((any_pwl, npol))])
              Hpol = hstack([csr_matrix((npol, any_pwl)), Hpol])
  #        if H is not None:
  #            H = hstack([csr_matrix((nw, any_pwl+npol)), H])
  
          HHw = vstack([h for h in [Hpwl, Hpol] if h is not None], "csr")
  
          CCw = r_[Cpwl, Cpol]
  
          ffparm = r_[fparm_pwl, fparm_pol]
  
          return NN, HHw, CCw, ffparm
docs: Combines pwl, polynomial and user-defined costs.