Update Rubocop todo

lib/active_model/serializer/adapter/json_api.rb

@@ -130,11 +130,14 @@ module ActiveModel
           end
         end
 
-        def included_for(serializer)
-          included.flat_map do |inc|
-            association = serializer.associations.find { |assoc| assoc.key == inc.first }
-            _included_for(association.serializer, inc.second) if association
-          end.uniq
+        def included_resources(include_tree)
+          included = []
+
+          serializer.associations(include_tree).each do |association|
+            add_included_resources_for(association.serializer, include_tree[association.key], included)
+          end
+
+          included
         end
 
         def add_included_resources_for(serializer, include_tree, included)

lib/active_model/serializer/include_tree.rb

@@ -16,9 +16,9 @@ module ActiveModel
           when Symbol
             { included => {} }
           when Hash
-            included.each_with_object({}) { |(key, value), hash|
+            included.each_with_object({}) do |(key, value), hash|
               hash[key] = include_args_to_hash(value)
-            }
+            end
           when Array
             included.reduce({}) { |a, e| a.merge!(include_args_to_hash(e)) }
           when String