anchor.diff:  
     This is useful for observing text fields while the user is typing.
   
  -  The unobtrusive variant of this is the [`up-observe`](/up-observe) attribute.
  +  The unobtrusive variant of this is the [`[up-observe]`](/up-observe) attribute.
   
     \#\#\# Example
   
  
positive.code:       })
  
    @function up.observe
    @param {string|Element|Array<Element>|jQuery} selectorOrElement
      The form fields that will be observed.
  
      You can pass one or more fields, a `<form>` or any container that contains form fields.
      The callback will be run if any of the given fields change.
    @param {number} [options.delay=up.form.config.observeDelay]
      The number of miliseconds to wait before executing the callback
      after the input value changes. Use this to limit how often the callback
  
negative.code:     A destructor function that removes the observe watch when called.
    @stable
    ###
    observe = (elements, args...) ->
      elements = e.list(elements)
      fields = u.flatMap(elements, findFields)
      callback = u.extractCallback(args) ? observeCallbackFromElement(elements[0]) ? up.fail('up.observe: No change callback given')
      options = u.extractOptions(args)
  