    * @return the extended session object
   ###
   extend: (session, subject, number) ->
-    return session if not session?
-
-    # Set the session subject property.
-    ###*
-     * The parent {{#crossLink "Subject"}}{{/crossLink}}.
-     * 
-     * @property subject {Object} 
-    ###
-    session.subject = subject
-
     # Set the session number property.
     ###*
      * The one-based subject session index in date order.
-     * 
-     * @property number {number} 
+     *
+     * @property number {number}
     ###
     session.number = number
 

       * @property title
      ###
      title:
        # TODO - get the Session title template from a labels.cfg
        # entry:
        #   [Session]
        #   label=Session
        # and include the label in the format below. Thus, the
        # title could be externally configurable to include, say,
        # 'Visit', rather than 'Session'. See also the subject.data.coffee
        # title TODO.
        get: ->
          "#{ @subject.title } Session #{ @number }"

      ###*
       * The [_parent_, {session: _session_}] path, where:

      path:
        get: ->
          @subject.path.concat([{session: @number }])

      ###*
       * The first modeling with a scan source.
       *
       * @property scanModeling
      ###
      scanModeling:
        get: ->
          _.find(@modelings, 'source.scan')

      ###*
       * The first modeling with a registration source.
       *
       * @property registrationModeling
      ###
      registrationModeling:
        get: ->
          _.find(@modelings, 'source.registration')

    ###*
     * @method hasDetailProperties
