It shows what `Vim` expects from a command. Initially, I wanted to move the `Command` class in commands.coffee here, but then I realized that it was too specific to fit there. For a while, the `Command` class extended `Vim.Command`, but currently it does not. So, no, it is not used anywhere. If you don't like unused code, we could comment it, or perhaps remove it. I think it is good documentation though.