code: public Map<String, byte[]> getCurrentMembers()
      {
          ImmutableMap.Builder<String, byte[]> builder = ImmutableMap.builder();
          boolean thisIdAdded = false;
          for ( ChildData data : cache.getCurrentData() )
          {
              String id = idFromPath(data.getPath());
              thisIdAdded = thisIdAdded || id.equals(thisId);
              builder.put(id, data.getData());
          }
          if ( !thisIdAdded )
          {
              builder.put(thisId, pen.getData());   // this instance is always a member
          }
          return builder.build();
      }
docs: Return the current view of membership. The keys are the IDs
  of the members. The values are each member's payload
  
  @return membership