docs: def run(self):
          """ Construct the document id from the date and the url. """
          document = {}
          document['_id'] = hashlib.sha1('%s:%s' % (
                                         self.date, self.url)).hexdigest()
          with self.input().open() as handle:
              document['content'] = handle.read().decode('utf-8', 'ignore')
          document['url'] = self.url
          document['date'] = unicode(self.date)
          with self.output().open('w') as output:
              output.write(json.dumps(document))