Remove deprecated test_helper decorator (#1013)

stripe/api_resources/abstract/__init__.py

@@ -27,7 +27,6 @@
 from stripe.api_resources.abstract.custom_method import custom_method
 
 from stripe.api_resources.abstract.test_helpers import (
-    test_helpers,
     APIResourceTestHelpers,
 )
 

stripe/api_resources/abstract/test_helpers.py

@@ -2,7 +2,6 @@
 
 from stripe import error
 from urllib.parse import quote_plus
-from stripe.api_resources.abstract import APIResource
 
 
 class APIResourceTestHelpers:
@@ -53,27 +52,3 @@ def instance_url(self):
         base = self.class_url()
         extn = quote_plus(id)
         return "%s/%s" % (base, extn)
-
-
-# TODO (next major)
-def test_helpers(cls):
-    """
-    The test_helpers decorator is deprecated and will be removed in a future version
-    of the library.
-    """
-
-    def test_helpers_getter(self):
-        return self.TestHelpers(self)
-
-    if not issubclass(cls, APIResource):
-        raise ValueError(
-            "Could not apply @test_helpers decorator to %r."
-            " The class should a subclass of APIResource." % cls
-        )
-
-    cls.TestHelpers._resource_cls = cls
-    cls.TestHelpers._static_request = cls._static_request
-    cls.TestHelpers._static_request_stream = cls._static_request_stream
-
-    cls.test_helpers = property(test_helpers_getter)
-    return cls