new_contents: from abc import ABCMeta, abstractmethod
  
  class Consensus(metaclass=ABCMeta):
      """
      An interface for defining a consensus protocol.
      The 'propose' and 'decide' methods need to be defined
      """
  
      @abstractmethod
      def propose(self, message):
          #raise NotImplementedError("Method 'propose' needs to be implemented")
          pass
  
      @abstractmethod
      def decide(self):
          #raise NotImplementedError("Method 'decide' needs to be implemented")
          pass
subject: Add abstract Consensus protocol class