code: @Override
      public void prepare(Map conf) {
          _admins = new HashSet<String>();
          _supervisors = new HashSet<String>();
          _nimbusUsers = new HashSet<String>();
          _nimbusGroups = new HashSet<String>();
  
          if (conf.containsKey(Config.NIMBUS_ADMINS)) {
              _admins.addAll((Collection<String>) conf.get(Config.NIMBUS_ADMINS));
          }
          if (conf.containsKey(Config.NIMBUS_SUPERVISOR_USERS)) {
              _supervisors.addAll((Collection<String>) conf.get(Config.NIMBUS_SUPERVISOR_USERS));
          }
          if (conf.containsKey(Config.NIMBUS_USERS)) {
              _nimbusUsers.addAll((Collection<String>) conf.get(Config.NIMBUS_USERS));
          }
  
          if (conf.containsKey(Config.NIMBUS_GROUPS)) {
              _nimbusGroups.addAll((Collection<String>) conf.get(Config.NIMBUS_GROUPS));
          }
  
          _ptol = AuthUtils.GetPrincipalToLocalPlugin(conf);
          _groupMappingProvider = AuthUtils.GetGroupMappingServiceProviderPlugin(conf);
      }
docs: Invoked once immediately after construction
  
  @param conf Storm configuration