code: def delete(self, conn, key):
          
          assert self._validate_key(key)
  
          command = b'delete ' + key + b'\r\n'
          response = yield from self._execute_simple_command(conn, command)
  
          if response not in (const.DELETED, const.NOT_FOUND):
              raise ClientException('Memcached delete failed', response)
          return response == const.DELETED
docs: Deletes a key/value pair from the server.
  
          :param key: is the key to delete.
          :return: True if case values was deleted or False to indicate
          that the item with this key was not found.