code: def get_write_fields(self):
          
  
          # Record specification fields
          rec_write_fields = self.get_write_subset('record')
  
          # Add comments if any
          if self.comments != None:
              rec_write_fields.append('comments')
  
          # Get required signal fields if signals are present.
          self.check_field('n_sig')
  
          if self.n_sig >  0:
              sig_write_fields = self.get_write_subset('signal')
          else:
              sig_write_fields = None
  
          return rec_write_fields, sig_write_fields
docs: Get the list of fields used to write the header, separating
          record and signal specification fields. Returns the default
          required fields, the user defined fields,
          and their dependencies.
  
          Does NOT include `d_signal` or `e_d_signal`.
  
          Returns
          -------
          rec_write_fields : list
              Record specification fields to be written. Includes
              'comment' if present.
          sig_write_fields : dict
              Dictionary of signal specification fields to be written,
              with values equal to the channels that need to be present
              for each field.