code: def add_document(self, key, url, **kwargs):
          
          document = self._check_metadata_for_file(key=key, url=url, **kwargs)
  
          for dict_key in (
              'description',
              'fulltext',
              'hidden',
              'material',
              'original_url',
              'url',
              'filename',
          ):
              if kwargs.get(dict_key):
                  document[dict_key] = kwargs[dict_key]
  
          if key_already_there(document, self.record.get('documents', ())):
              raise ValueError(
                  'There\'s already a document with the key %s.'
                  % document['key']
              )
  
          self._append_to('documents', document)
docs: Adds document to record
          Args:
              key (string): document key
              url (string): document url
          Keyword Args:
              description (string): simple description
              fulltext (bool): mark if this is a full text
              hidden (bool): is document should be hidden
              material (string):
              original_url (string): original url
              filename (string): current url
  
  
          Returns: None