Represents the condition function passed on the Scrubber.when.
@constructor

@param {Scrubber} sender - The sender scrubber
@param {object} parent - The parent object
@param {string} key - The property key
@param {any} value - The property value

@property {object} parent - The parent object
@property {string} key - The property key
@property {any} value - The property value
function (sender, parent, key, value) {
  this.scrubber = sender
  this.parent = parent
  this.key = key
  this.value = value
}