code: def _private_notes(self, key, value):
      
      def _is_for_cds(value):
          normalized_c_values = [el.upper() for el in force_list(value.get('c'))]
          return 'CDS' in normalized_c_values
  
      def _is_for_hal(value):
          normalized_c_values = [el.upper() for el in force_list(value.get('c'))]
          return 'HAL' in normalized_c_values
  
      def _is_not_for_hal(value):
          normalized_c_values = [el.upper() for el in force_list(value.get('c'))]
          return 'NOT HAL' in normalized_c_values
  
      _private_notes = self.get('_private_notes', [])
      _export_to = self.get('_export_to', {})
  
      for value in force_list(value):
          if _is_for_cds(value):
              _export_to['CDS'] = True
  
          if _is_for_hal(value):
              _export_to['HAL'] = True
          elif _is_not_for_hal(value):
              _export_to['HAL'] = False
  
          source = force_single_element(value.get('9'))
          for _private_note in force_list(value.get('a')):
              _private_notes.append({
                  'source': source,
                  'value': _private_note,
              })
  
      self['_export_to'] = _export_to
      return _private_notes
docs: Populate the ``_private_notes`` key.
  
      Also populates the ``_export_to`` key through side effects.