code: def create_nodata_node(self, valid_seg, tags=None):
          
          if tags is None:
              tags = []
          node = Node(self)
  
          # Set the output file
          # Add the PSD file if needed
          if self.write_psd:
              node.new_output_file_opt(valid_seg, '.txt', '--psd-output',
                                       tags=tags+['PSD_FILE'], store_file=self.retain_files)
  
          node.new_output_file_opt(valid_seg, '.xml.gz', '--output-file',
                                   store_file=self.retain_files)
  
          if self.psd_files is not None:
              should_add = False
  
              # If any of the ifos for this job are in the set
              # of ifos for which a static psd was provided.
              for ifo in self.ifo_list:
                  for psd_file in self.psd_files:
                      if ifo in psd_file.ifo_list:
                          should_add = True
  
              if should_add:
                  node.add_input_opt('--psd-file', psd_file)
  
          return node
docs: A simplified version of create_node that creates a node that does not
          need to read in data.
  
          Parameters
          -----------
          valid_seg : glue.segment
              The segment over which to declare the node valid. Usually this
              would be the duration of the analysis.
  
          Returns
          --------
          node : pycbc.workflow.core.Node
              The instance corresponding to the created node.