error: unexpected flake input attribute 'submodules' when using submodules

[flyingpeakock]

If inputs.self.submodules = true nix-inspect crashes shortly after starting.
Needed to include submodules in the flake.

[RetoranPetra]

This is a problem for my configuration as well, as my neovim configuration is a git submodule

[RetoranPetra]

Here is the error I get from the termination (I have edited the whitespace for clarity as it displayed with odd whitespace at the bottom of the TUI):

terminate called after throwing an instance of 'nix::Error'
what():  error:
… while calling the 'getFlake' builtin
            at «string»:1:1:
                                        1| builtins.getFlake "/etc/nixos"
                                                                                      | ^
 error: unexpected flake input attribute 'submodules', at /nix/store/98gj8ib5xb81zkm97vglcq8rmn2jxp6w-source/flake.nix:18:5

and line 18 refers to

{
  inputs = {
    ...
    self.submodules = true;
    ...
  };
}