# File lib/nokogiri/xml/node.rb, line 576
      def namespace= ns
        return set_namespace(ns) unless ns

        unless Nokogiri::XML::Namespace === ns
          raise TypeError, "#{ns.class} can't be coerced into Nokogiri::XML::Namespace"
        end
        if ns.document != document
          raise ArgumentError, 'namespace must be declared on the same document'
        end

        set_namespace ns
      end