```coffeescript
Impromptu = require '../impromptu'

class Instance extends Impromptu.Cache
  run: (fn) ->
    return get fn if @_cached

    @set (err, results) =>
      if err then fn err else @get fn


  get: (fn) ->
    fn null, @_cached ? @options.fallback


  set: (fn) ->
    @options.update.call @options.context, (err, value) =>
      unless err
        @_cached = value
      fn err, !err


  unset: (fn) ->
    @_cached = null
    fn null, true


# Expose `Instance`.
exports = module.exports = Instance
```

Add missing reference to this.
user
```coffeescript
Impromptu = require '../impromptu'

class Instance extends Impromptu.Cache
  run: (fn) ->
    return @get fn if @_cached

    @set (err, results) =>
      if err then fn err else @get fn


  get: (fn) ->
    fn null, @_cached ? @options.fallback


  set: (fn) ->
    @options.update.call @options.context, (err, value) =>
      unless err
        @_cached = value
      fn err, !err


  unset: (fn) ->
    @_cached = null
    fn null, true


# Expose `Instance`.
exports = module.exports = Instance
```
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