package AB;

message A {
  optional string name = 1;
  extensions 2 to max;

  extend B { optional A akeyba = 11; }
}

message B {
  optional string name = 1;
  extensions 2 to max;

  extend A { optional B bkeyab = 21; }
}


extend A {
  repeated B keyab = 41;
  repeated A keyaa = 42;
}

extend B {
  repeated A keyba = 43;
  repeated B keybb = 44;
}