code: public static int registerDiagnosticModule(DiagnosticModule diagnosticModule, String packageName) {
          if (modules.containsKey(packageName)) {
              return 1;
          }
  
          try {
              diagnosticModule.init();
          } catch (Throwable th) {
              // No FFDC code needed - we're reporting the problem to our caller
              // (Note: the server version doesn't FFDC either...)
              return 3;
          }
  
          modules.put(packageName, diagnosticModule);
          return 0;
      }
docs: Register a diagnostic module
  
  @param diagnosticModule
  The diagnostic module to be registered
  @param packageName
  The package name with which to register
  @return 0 if the diagnostic module is registered 1 if the diagnostic
  module was already registered 3 if the diagnostic module could
  not be initialized