docs: def _compile_pfgen(self):
          """Post power flow computation for PV and SW"""
          string = '"""\n'
          string += 'system.dae.init_g()\n'
          for gcall, pflow, shunt, series, stagen, call in zip(
                  self.gcall, self.pflow, self.shunt, self.series, self.stagen,
                  self.gcalls):
              if gcall and pflow and (shunt or series) and not stagen:
                  string += call
          string += '\n'
          string += 'system.dae.reset_small_g()\n'
          string += '"""'
          self.pfgen = compile(eval(string), '', 'exec')