docs: protected OmemoRatchet<T_IdKeyPair, T_IdKey, T_PreKey, T_SigPreKey, T_Sess, T_Addr, T_ECPub, T_Bundle, T_Ciph>
      getOmemoRatchet(OmemoManager manager) {
          OmemoRatchet<T_IdKeyPair, T_IdKey, T_PreKey, T_SigPreKey, T_Sess, T_Addr, T_ECPub, T_Bundle, T_Ciph>
                  omemoRatchet = omemoRatchets.get(manager);
          if (omemoRatchet == null) {
              omemoRatchet = instantiateOmemoRatchet(manager, omemoStore);
              omemoRatchets.put(manager, omemoRatchet);
          }
          return omemoRatchet;
      }