Failed to load the css-edit-groups package

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[Enter steps to reproduce:]

1. ...
2. ...

**Atom**: 1.33.0 x64
**Electron**: 2.0.11
**OS**: Unknown Windows version
**Thrown From**: [css-edit-groups](https://github.com/ekonstantinidis/css-edit-groups) package 0.4.2

### Stack Trace

Failed to load the css-edit-groups package

```
At Duplicate key 'cmd-l'

Error: Duplicate key 'cmd-l'
at Object.r (:11:581828)
at addProperty (:14:1904257)
at Array.reduce (:null:null)
at Obj (:14:1903923)
at transformNode (:14:1905297)
at Value (:14:1903171)
at transformNode (:14:1905297)
at addProperty (:14:1904245)
at Array.reduce (:null:null)
at Obj (:14:1903923)
at transformNode (:14:1905297)
at Value (:14:1903171)
at transformNode (:14:1905297)
at Block (:14:1903129)
at transformNode (:14:1905297)
at Object.parse (:14:1905318)
at m (:11:579071)
at c (:11:579277)
at Object.readFileSync (:11:580370)
at keymaps.getKeymapPaths.map.e (:11:3032546)
at Array.map (:null:null)
at Package.loadKeymaps (:11:3032534)
at measure (:11:3026088)
at Package.measure (:11:3025283)
at Package.load (:11:3026024)
at PackageManager.loadAvailablePackage (:11:381123)
at config.transact (:11:379546)
at Config.transact (:11:332082)
at PackageManager.loadPackages (:11:379484)
at t.loadState.then (:1:647009)
at :null:null

```

### Commands

```
```

### Non-Core Packages

```
aligner-scss 1.3.1
atom-beautify 0.33.4
atom-bootstrap4 1.4.0
atom-clock 0.1.16
atom-css-comb 3.3.1
atom-css-unit-converter 1.1.1
atom-dark-minimal-ui 0.5.8
atom-debug-ui 1.0.4
atom-email-snippets 0.1.0
atom-ide-ui 0.13.0
atom-linter-phpstan 1.0.2
atom-sass 0.4.0
atom-typescript 12.7.2
autocomplete-php 0.3.7
autoprefixer 3.7.1
caniuse-css 1.1.5
coffee-compile 0.31.0
color-picker 2.3.0
css-edit-groups 0.4.2
css-grid-snippets 1.1.1
css-snippets 1.1.0
css-spy 0.6.0
docblockr 0.13.7
double-tag 1.5.0
emmet 2.4.3
es6-javascript 1.0.0
flexbox-snippets 0.3.0
git-plus 8.1.0
git-time-machine 2.1.0
goto-definition 1.3.4
highlight-selected 0.14.0
html-to-css 0.2.2
javascript-snippets 1.2.1
language-babel 2.85.0
linter 2.2.0
linter-bootlint 1.1.0
linter-csslint 2.0.1
linter-eslint 8.4.1
linter-htmlhint 1.5.1
linter-liferay 3.0.0
linter-php 1.5.1
linter-sass-lint 1.8.3
MavensMate-Atom 1.1.0
merge-conflicts 1.4.5
minimap 4.29.9
minimap-autohider 1.5.4
minimap-bookmarks 0.4.2
minimap-highlight-selected 4.6.1
minimap-linter 2.2.1
minimap-pigments 0.2.2
oceanic-next 1.0.0
php-cs-fixer 4.1.1
php-debug 0.3.5
php-server 0.8.0
phpunit-snippets 0.1.0
pigments 0.40.2
project-manager 3.3.6
remote-edit 1.9.0
sass-comment 1.4.0
scss-snippets 0.6.0
semantic-ui 1.0.9
sync-settings 0.8.6
terminal-like-syntax 0.11.0
terminal-syntax 0.1.0
todo-show 2.3.2
w3c-validation 0.4.0
```

Reproduce the failure by enabling css-edit-groups 0.4.2 in Atom 1.33.0 and start at the Package.loadKeymaps entry shown in the stack trace. Inspect the package's keymap files for the reported duplicate cmd-l binding. Done means the package loads without the duplicate-key error.

Written by the indexing model from the issue text.