code: def attach(self, id, filename, url):
          
          Attachment = self.client.model('ir.attachment')
          return Attachment.add_attachment_from_url(
              filename, url, '%s,%s' % (self.model_name, id)
          )
docs: Add an attachmemt to record from url
  
          :param id: ID of record
          :param filename: File name of attachment
          :param url: Public url to download file from.