Custom script for collective.easyform


I want to know how to handle the problem below.
We use the custom script of collective.easyform for generating automatic replies as a receipt for the respondents.
In the email body, I want to add "field_lable" in Japanese instead of "field_id" as the titles of the answer's contents, but we couldn't find the way.

If you have any solution for this, could you give us the advice?

message = ""
reply_addr = ""
for field_id, value in fields.items():
if field_id == "form.widgets.replyto":
reply_addr = value
elif field_id == "":
message = value + message
message += field_id + ": " + value + "\n"

What is the specific problem? Determine the language?