code: function packageStatesSerialize () {
    if (atom.packages.serialize != null) {
      return atom.packages.serialize()
    }
  
    atom.packages.getActivePackages().forEach((pack) => {
      var state
      if (pack.serialize != null) state = pack.serialize()
      if (state) {
        atom.packages.setPackageState(pack.name, state)
      }
    })
  
    return atom.packages.packageStates
  }
docs: shim atom.packages.serialize in <= 1.6