code: def delete(self, key, return_previous=None, timeout=None):
          
          assembler = commons.DeleteRequestAssembler(self._url, key, return_previous)
  
          obj = yield self._post(assembler.url, assembler.data, timeout)
  
          deleted = Deleted._parse(obj)
  
          returnValue(deleted)
docs: Delete value(s) from etcd.
  
          :param key: key is the first key to delete in the range.
          :type key: bytes or instance of :class:`txaioetcd.KeySet`
  
          :param return_previous: If enabled, return the deleted key-value pairs
          :type return_previous: bool or None
  
          :param timeout: Request timeout in seconds.
          :type timeout: int
  
          :returns: Deletion info
          :rtype: instance of :class:`txaioetcd.Deleted`