def attributes(instance)
      definitions.values.each_with_object({}) do |item, obj|
        key = item.target
        val = instance.send(:instance_variable_get, item.ivar)
        obj[key] = val unless null == val
      end
    end
def attributes(instance)
      definitions.values.each_with_object({}) do |item, obj|
        key = item.target
        val = instance.send(:instance_variable_get, item.ivar)
        obj[key] = val unless null == val
      end
    end
The hash of assigned attributes for an instance of the [#extended_class]
 @param  [Dry::Initializer::Instance] instance
 @return [Hash<Symbol, Object>]