_assign_attribute

# File activemodel/lib/active_model/attribute_assignment.rb, line 46
      def _assign_attribute(k, v)
        setter = :"#{k}="
        public_send(setter, v)
      rescue NoMethodError
        if respond_to?(setter)
          raise
        else
          raise UnknownAttributeError.new(self, k.to_s)
        end
      end