refactor(frontends/lean/structure_cmd): some more cleanup
refactor(frontends/lean/structure_cmd): some more cleanup

rlewis1988/lean,fpvandoorn/lean,dselsam/lean,rlewis1988/lean,leanprover/lean,digama0/lean,fpvandoorn/lean,johoelzl/lean,johoelzl/lean,leodemoura/lean,johoelzl/lean,leanprover/lean,fpvandoorn/lean,Kha/lean,rlewis1988/lean,leodemoura/lean,leanprover/lean,digama0/lean,dselsam/lean,avigad/lean,fpvandoorn/lean,rlewis1988/lean,leanprover/lean,Kha/lean,rlewis1988/lean,avigad/lean,fpvandoorn/lean,digama0/lean,Kha/lean,leodemoura/lean,avigad/lean,johoelzl/lean,digama0/lean,Kha/lean,rlewis1988/lean,dselsam/lean,leanprover-community/lean,avigad/lean,leanprover/lean,avigad/lean,leanprover-community/lean,johoelzl/lean,dselsam/lean,fpvandoorn/lean,leodemoura/lean,leodemoura/lean,johoelzl/lean,digama0/lean,leanprover-community/lean,dselsam/lean,avigad/lean,digama0/lean,Kha/lean,leanprover-community/lean,dselsam/lean,leanprover-community/lean,leanprover-community/lean,leodemoura/lean,leanprover/lean,Kha/lean