code: def copyright(self, key, value):
      
      MATERIAL_MAP = {
          'Article': 'publication',
          'Published thesis as a book': 'publication',
      }
  
      material = value.get('e') or value.get('3')
  
      return {
          'holder': value.get('d'),
          'material': MATERIAL_MAP.get(material),
          'statement': value.get('f'),
          'url': value.get('u'),
          'year': maybe_int(value.get('g')),
      }
docs: Populate the ``copyright`` key.