Failure to select elements within an iframe

The filter is unable to select elements within an iframe using css or xpath. Judging from [this](https://stackoverflow.com/questions/28814916/how-do-i-select-elements-inside-an-iframe-with-xpath) stackoverflow question/answer, it may be feasable to add a workaround where you can 'shift' the current context of the xpath/css to an iframe's xpath. 