code: def test_url_for_with_self(self, app, req_ctx):
      @app.route("/<self>")
      def index(self):
          return "42"
  
      assert flask.url_for("index", self="2") == "/2"
  
imports: import io
  import os
  import pytest
  import werkzeug.exceptions
  import flask
  from flask.helpers import get_debug_flag
label_desc: Use image node_id 6 for calling the TestUrlFor obj's underlying member method code with example usage: obj.test_url_for_with_self(app, req_ctx) and returns: str