feat: update ChatMessage type with 'refusal' and 'content' is now opt…

…ional

src/types.ts

@@ -22,8 +22,14 @@ export type ToolCall = {
 };
 
 export type ChatMessage = {
-  /** The contents of the message. `content` is required for all messages, and may be null for assistant messages with function calls. */
-  content: string | null;
+  /**
+   * The contents of the message. `content` may be null for assistant messages
+   * with function calls or `undefined` for assistant messages if a `refusal`
+   * was given by the model.
+   */
+  content?: string | null;
+  /** The refusal message generated by the model. */
+  refusal?: string | null;
   /** The role of the messages author. One of `system`, `user`, `assistant`, 'tool', or `function`. */
   role: Role;
   /** The name and arguments of a function that should be called, as generated by the model. */