Rather than doing this check while looping through the elements, we should just do this before starting the element loop:
```
# Remove all default styling from headers
for style_id, styles in self.styles_dict.items():
    if styles['style_name'].lower() in headers:
        if 'default_run_properties' in styles:
            del self.styles_dict[style_id]['default_run_properties']
```

I think that's the way the nesting works, but either way, we should be able to do this once looping through 10 items rather than potentially once per header in the document.