docs: @Override
      public Principal getCallerPrincipal()
      {
          EJBSecurityCollaborator<?> securityCollaborator = container.ivSecurityCollaborator;
          if (securityCollaborator == null)
          {
              return NullSecurityCollaborator.UNAUTHENTICATED;
          }
  
          return getCallerPrincipal(securityCollaborator, EJSContainer.getMethodContext());
      }