function isMessage(
  obj: any,
): obj is {
  content:
    | string
    | ({ text: string; type: "text" } | { file_id: string; type: "file" })[];
  role:
    | "function"
    | "agent"
    | "tool"
    | "assistant"
    | "developer"
    | "system"
    | "user";
  tool_call_id?: null | string;
  tool_calls?:
    | null
    | { function: { arguments: string; name: string }; id: string }[];
};