code: def _build_url_rewriter(cls, session: AppSession):
          '''Build URL rewriter if needed.'''
          if session.args.escaped_fragment or session.args.strip_session_id:
              return session.factory.new(
                  'URLRewriter',
                  hash_fragment=session.args.escaped_fragment,
                  session_id=session.args.strip_session_id
              f _build_url_rewriter(cls, session: AppSession):
          '''Build URL rewriter if needed.'''
          if session.args.escaped_fragment or session.args.strip_session_id:
              return session.factory.new(
                  'URLRewriter',
                  hash_fragment=session.args.escaped_fragment,
                  session_id=session.args.strip_session_id
              )
docs: Build URL rewriter if needed.