def get_async_doc(id, opts = {})
      data, _status_code, _headers = get_async_doc_with_http_info(id, opts)
      return data
    end
def get_async_doc(id, opts = {})
      data, _status_code, _headers = get_async_doc_with_http_info(id, opts)
      return data
    end
Downloads a document.
 @param id The download_id returned from status request or a callback.
 @param [Hash] opts the optional parameters
 @return [String]