code: public static Collection<ICredentialsRenewer> GetCredentialRenewers(Map conf) {
          try {
              Set<ICredentialsRenewer> ret = new HashSet<ICredentialsRenewer>();
              Collection<String> clazzes = (Collection<String>) conf.get(Config.NIMBUS_CREDENTIAL_RENEWERS);
              if (clazzes != null) {
                  for (String clazz : clazzes) {
                      ICredentialsRenewer inst = (ICredentialsRenewer) Class.forName(clazz).newInstance();
                      inst.prepare(conf);
                      ret.add(inst);
                  }
              }
              return ret;
          } catch (Exception e) {
              throw new RuntimeException(e);
          }
      }
docs: Get all of the configured Credential Renwer Plugins.
  
  @param storm_conf the storm configuration to use.
  @return the configured credential renewers.