Message.Content_partmodule Image_url : sig ... endmodule File_data : sig ... endval sexp_of_t : t -> Sexplib0.Sexp.tval text : string -> tval image_base64 : mime_type:string -> data:string -> tmime_type should be e.g. "image/jpeg", "image/png", "image/webp", "image/gif"
val file : filename:string -> file_data:string -> tfile_data can be either a URL (for publicly accessible files) or a data URL like "data:application/pdf;base64,..." for local files