fixes #24 (type checking in backend)
fixes #24 (type checking in backend)

iclab/centinel-server,iclab/centinel-server,lianke123321/centinel-server,rpanah/centinel-server,lianke123321/centinel-server,iclab/centinel-server,ben-jones/centinel-server,rpanah/centinel-server,lianke123321/centinel-server,rpanah/centinel-server,ben-jones/centinel-server,ben-jones/centinel-server