[NTG-context] A question about the node library in luatex

I am trying a few tests with luatex. 1. Made a format file "luaetex.fmt" by "luatex --ini etex.ini" and a lua file "luaetex.lua" containing just one line "node.types()" 2. Test file "test.tex" is as follows: \directlua0{node.types()} \bye 3. Run "luatex --fmt=luaetex.fmt test". Then there is no problem. 4. Instead, "luatex --lua=luaetex.lua --fmt=luaetex.fmt test" causes an error. Why don't we use the node library in the lua file "luaetex.lua"? Thanks in advance, ChoF.