code: def unshare_database(self, username):
          
          doc = self.security_document()
          data = doc.get('cloudant', {})
          if username in data:
              del data[username]
          doc['cloudant'] = data
          resp = self.r_session.put(
              self.security_url,
              data=json.dumps(doc, cls=self.client.encoder),
              headers={'Content-Type': 'application/json'}
          )
          resp.raise_for_status()
          return response_to_json_dict(resp)
docs: Removes all sharing with the named user for the current remote database.
          This will remove the entry for the user from the security document.
          To modify permissions, use the
          :func:`~cloudant.database.CloudantDatabase.share_database` method
          instead.
  
          :param str username: Cloudant user to unshare the database from.
  
          :returns: Unshare database status in JSON format