Why does the request.META does not include "HTTP-IF-NONE-MATCH" when I have set the ETAG in the response in Django?

Question

The code of the response is as below:

response=HttpResponse("hello")
response["ETag"] = "4526A5E1A79DE447F21500A0E43B301A"
return response

There is not any information about IF-NONE-MATCH in the next request.META.

Can someone tell me why and how?