bpo-37648: Fixed minor inconsistency in some __contains__. (GH-14904)

The collection's item is now always at the left and
the needle is on the right of ==.
diff --git a/Doc/library/test.rst b/Doc/library/test.rst
index da6a85d..6eef5c6 100644
--- a/Doc/library/test.rst
+++ b/Doc/library/test.rst
@@ -367,6 +367,12 @@
    Object that is equal to anything.  Used to test mixed type comparison.
 
 
+.. data:: NEVER_EQ
+
+   Object that is not equal to anything (even to :data:`ALWAYS_EQ`).
+   Used to test mixed type comparison.
+
+
 .. data:: LARGEST
 
    Object that is greater than anything (except itself).