public String getDSMembership() {
    if (identity == null) {
      // some unit tests create IDs that have no real identity, so return null
      return "null";
    }
    // don't cache if we haven't connected to the server yet
    if (((InternalDistributedMember) getDistributedMember()).getMembershipPort() == 0) {
      return getMemberIdAsString();
    }
    if (memberIdString == null) {
      memberIdString = getMemberIdAsString();
    }
    return memberIdString;
  }
returns a string representation of this identifier, ignoring the toString cache
geode-core/src/main/java/org/apache/geode/internal/cache/tier/sockets/ClientProxyMembershipID.java