What is the signature of legendary.keymap function?

[towry]

https://github.com/mrjones2014/legendary.nvim/blob/master/doc/API.md

The doc seems not provide detailed signature of keymap, I thought it is same as vim.keymap.set, but I got errors just replace vim.keymap.set with legendary.keymap

Error detected while processing /Users/towry/.config/nvim/init.lua:                
E5113: Error while calling lua chunk: ...acker/start/legendary.nvim/lua/legendary/d
ata/keymap.lua:36: 1: expected string, got nil                                     
stack traceback:                                                                   
        [C]: in function 'error'                                                   
        vim/shared.lua: in function 'validate'                                     
        ...acker/start/legendary.nvim/lua/legendary/data/keymap.lua:36: in function
 'parse'                                                    

[mrjones2014]

It accepts a legendary.nvim keymap table.

https://github.com/mrjones2014/legendary.nvim/blob/master/doc/table_structures/KEYMAPS.md