Styler extremely slow
#### Code Sample

```python
def highlighter(col):
    '''
    Highlights rows in `highlight_map` keys where df[`highlight map` values]==1
    '''

    highlight_map = {
        'Service Type': 'ServiceType_Added',
        'Store #': 'Store_Added',
    }
    if col.name in highlight_map:
        return ['background-color: yellow' if final[highlight_map[col.name]][v] else '' for v in col.index.tolist()]
    else:
        return [''] * len(col)
    
styled = final.style.apply(highlighter)
styled.to_excel('highlights.xlsx', engine='openpyxl') 

```
#### Problem description

Here I have some conditional highlighting on a df with 18k rows. The issue is that despite preceding complex operations on the df (such as conditional merges and `df.apply` by row) taking ~300ms at the most, the `Styler.apply` part takes over two minutes. I realize this feature is in development but I am wondering if there is a way to make it faster or if this is a known issue. 



