code: def write_xsd(cls) -> None:
          
          with open(cls.filepath_source) as file_:
              template = file_.read()
          template = template.replace(
              '<!--include model sequence groups-->', cls.get_insertion())
          template = template.replace(
              '<!--include exchange items-->', cls.get_exchangeinsertion())
          with open(cls.filepath_target, 'w') as file_:
              file_.write(template)
docs: Write the complete base schema file `HydPyConfigBase.xsd` based
          on the template file `HydPyConfigBase.xsdt`.
  
          Method |XSDWriter.write_xsd| adds model specific information to the
          general information of template file `HydPyConfigBase.xsdt` regarding
          reading and writing of time series data and exchanging parameter
          and sequence values e.g. during calibration.
  
          The following example shows that after writing a new schema file,
          method |XMLInterface.validate_xml| does not raise an error when
          either applied on the XML configuration files `single_run.xml` or
          `multiple_runs.xml` of the `LahnH` example project:
  
          >>> import os
          >>> from hydpy.auxs.xmltools import XSDWriter, XMLInterface
          >>> if os.path.exists(XSDWriter.filepath_target):
          ...     os.remove(XSDWriter.filepath_target)
          >>> os.path.exists(XSDWriter.filepath_target)
          False
          >>> XSDWriter.write_xsd()
          >>> os.path.exists(XSDWriter.filepath_target)
          True
  
          >>> from hydpy import data
          >>> for configfile in ('single_run.xml', 'multiple_runs.xml'):
          ...     XMLInterface(configfile, data.get_path('LahnH')).validate_xml()