whole_func_string: function getCallback (o) {
                      var last = libs.object.last(o);
                      return last instanceof Function ? last : NULL_FUNCTION;
                  }
func_code_string: function getCallback (o) {
                      var last = libs.object.last(o);
                      return last instanceof Function ? last : NULL_FUNCTION;
                  }
func_documentation_string: If the last item in the object is a function, it will be returned. Otherwise, an "empty" function will be returned.
  Useful for ensuring that a callback can always be invoked, without checking if the argument is a function
  over and over.
  @param {Object} o The object to get the callback for.
  @return {Function} If the last item in the object is a function, it will be returned. Otherwise, an "empty" function will be returned.