code: func GetPerRPCCredentials(kind RPCAuthorityKind, opts ...RPCOption) (credentials.PerRPCCredentials, error) {
  	options, err := makeRPCOptions(kind, opts)
  	if err != nil {
  		return nil, err
  	}
  	return perRPCCreds{options}, nil
  }
docs: // GetPerRPCCredentials returns gRPC's PerRPCCredentials implementation.
  //
  // It can be used to authenticate outbound gPRC RPC's.