code: func (ethash *Ethash) APIs(chain consensus.ChainReader) []rpc.API {
  	// In order to ensure backward compatibility, we exposes ethash RPC APIs
  	// to both eth and ethash namespaces.
  	return []rpc.API{
  		{
  			Namespace: "eth",
  			Version:   "1.0",
  			Service:   &API{ethash},
  			Public:    true,
  		},
  		{
  			Namespace: "ethash",
  			Version:   "1.0",
  			Service:   &API{ethash},
  			Public:    true,
  		},
  	}
  }
docs: // APIs implements consensus.Engine, returning the user facing RPC APIs.