code: def delete(self, key, cas=0):
          
          returns = []
          for server in self.servers:
              returns.append(server.delete(key, cas))
  
          return any(returns)
docs: Delete a key/value from server. If key does not exist, it returns True.
  
          :param key: Key's name to be deleted
          :param cas: CAS of the key
          :return: True in case o success and False in case of failure.