code: def save_series(self) -> None:
          
          hydpy.pub.sequencemanager.open_netcdf_writer(
              flatten=hydpy.pub.options.flattennetcdf,
              isolate=hydpy.pub.options.isolatenetcdf)
          self.prepare_sequencemanager()
          for sequence in self._iterate_sequences():
              sequence.save_ext()
          hydpy.pub.sequencemanager.close_netcdf_writer()
docs: Save time series data as defined by the actual XML `writer`
          element.
  
          >>> from hydpy.core.examples import prepare_full_example_1
          >>> prepare_full_example_1()
  
          >>> from hydpy import HydPy, TestIO, XMLInterface
          >>> hp = HydPy('LahnH')
          >>> with TestIO():
          ...     hp.prepare_network()
          ...     hp.init_models()
          ...     interface = XMLInterface('single_run.xml')
          ...     interface.update_options()
          >>> interface.update_timegrids()
          >>> series_io = interface.series_io
          >>> series_io.prepare_series()
          >>> hp.elements.land_dill.model.sequences.fluxes.pc.series[2, 3] = 9.0
          >>> hp.nodes.lahn_2.sequences.sim.series[4] = 7.0
          >>> with TestIO():
          ...     series_io.save_series()
          >>> import numpy
          >>> with TestIO():
          ...     os.path.exists(
          ...         'LahnH/series/output/land_lahn_2_flux_pc.npy')
          ...     os.path.exists(
          ...         'LahnH/series/output/land_lahn_3_flux_pc.npy')
          ...     numpy.load(
          ...         'LahnH/series/output/land_dill_flux_pc.npy')[13+2, 3]
          ...     numpy.load(
          ...         'LahnH/series/output/lahn_2_sim_q_mean.npy')[13+4]
          True
          False
          9.0
          7.0