Define Hash.ruby2_keywords_hash? singleton method

Author: nobu

lib/ruby2_keywords.rb

@@ -22,9 +22,9 @@ def ruby2_keywords
   end
 end
 
-class Hash
+class << Hash
   unless method_defined?(:ruby2_keywords_hash?)
-    def ruby2_keywords_hash?
+    def ruby2_keywords_hash?(hash)
       false
     end
   end