  
  from django.core.exceptions import DisallowedHost
  from django.core.handlers.wsgi import LimitedStream, WSGIRequest
  from django.http import HttpRequest, RawPostDataException, UnreadablePostError
  from django.http.request import split_domain_port
  from django.test import RequestFactory, SimpleTestCase, override_settings
  from django.test.client import FakePayload
  
  
  class RequestsTests(SimpleTestCase):
 
</s> remove from django.utils.datastructures import ImmutableList, MultiValueDict
 </s> add from django.utils.datastructures import (
    CaseInsensitiveMapping, ImmutableList, MultiValueDict,
) </s> remove     DictWrapper, ImmutableList, MultiValueDict, MultiValueDictKeyError,
    OrderedSet,
 </s> add     CaseInsensitiveMapping, DictWrapper, ImmutableList, MultiValueDict,
    MultiValueDictKeyError, OrderedSet, </s> remove * ...
 </s> add * Added :attr:`.HttpRequest.headers` to allow simple access to a request's
  headers.
from django.http.request import HttpHeaders, split_domain_port
  
  from django.core.exceptions import DisallowedHost
  from django.core.handlers.wsgi import LimitedStream, WSGIRequest
  from django.http import HttpRequest, RawPostDataException, UnreadablePostError
from django.http.request import HttpHeaders, split_domain_port
  from django.test import RequestFactory, SimpleTestCase, override_settings
  from django.test.client import FakePayload
  
  
  class RequestsTests(SimpleTestCase):
keep keep keep keep replace keep keep keep keep keep
 Fixed #20147 -- Added HttpRequest.headers. 
tests/requests/tests.py