README.md in koine-attributes-0.3.2 vs README.md in koine-attributes-0.4.0

@@ -116,9 +116,15 @@
     attribute :price, MyCustom::Money.new
     attribute :available, :boolean, ->(attribues){ attributes.with_default_value(true) }
     attribute :available, Koine::Attributes::Drivers::Boolean.new.with_default_value(true)
     attribute :tags, array_of(:string)
     attribute :config, hash_of(:symbol, :string)
+
+    # if you want to costumize the above
+    attribute :config, hash_of(:symbol, :string) do |adapter|
+      adapter.for_keys.with_nil_value
+      adapter.for_values.with_nil_value
+    end
   end
 end
 
 product = Product.new