Would it be useful to have the following helper method?
```python
def get_element_selector(self, video_display_name, class_name):
  return '{vertical} {video_element}'.format(
     vertical=self.get_video_vertical_css(video_display_name),
     video_element=class_name
 )
```
and use it so:
```python
captions_css = self.get_element_selector(video_display_name, CSS_CLASS_NAMES['captions_text']))
```