Copybara import of the project:

--
f8a3bdf by Oleksii Oleniuk <58557113+oleksii-oleniuk-star@users.noreply.github.com>:

fix: Add Context Cache support for ChatSessionPreview class (#433)

* add content cache to chat session

* remove logs, add gitignore

---------

Co-authored-by: Oleksii Oleniuk <oleksii.olenyuk@gmail.com>
Co-authored-by: Yvonne Yu <150068659+yyyu-google@users.noreply.github.com>
--
64ac1a8 by Wenhao <wenhao.zhan18@gmail.com>:

Fixed link in Part JSDoc

COPYBARA_INTEGRATE_REVIEW=#440 from WenHaozhan:fix/part-jsdoc 16bb232
PiperOrigin-RevId: 686218863

src/types/content.ts

@@ -459,8 +459,6 @@ export declare interface UsageMetadata {
   candidatesTokenCount?: number;
   /** Optional. Total number of tokens. */
   totalTokenCount?: number;
-  /** Optional. Number of tokens in the cached content. */
-  cachedContentTokenCount?: number;
 }
 
 /**