Working with theme

Let's say I am working on a new site call 'new_site', it may contains some different styles. Here is the example structure in the ui package which style1, style2 and style3 are folders for different layout styles.

.
+-- new_site
| +-- style1
| | +-- theme.ts
| +-- style2
| | +-- theme.ts
| +-- style3
| | +-- theme.ts
+-- sui-base
| +-- baseTheme.ts

All theme.ts files in the folder new_site/style** will be extends the baseTheme.ts file