Unable to display search filter in individual column header using vuetify datatable

问题

I'm trying to display text box in every column header for search filter using vuetify datatable. I modify the code in codepen. I'm able to show expected result in codepen. But when I used the same code in my IDE, it does not work. Datatable is displayed but text field doesnot displayed in my browser. I took reference from this link

``` 
https://codepen.io/fontzter/pen/qywQjK?editors=1010 
``` 

I replace following select box with text field in codepen code.

Select box code

Text field code

Please help me. Expected result

Actual result

来源：https://stackoverflow.com/questions/60897227/unable-to-display-search-filter-in-individual-column-header-using-vuetify-datata