code: def test_lookaround(self, test_env_async):
      tmpl = test_env_async.from_string(
          """{% for item in seq -%}
              {{ loop.previtem|default('x') }}-{{ item }}-{{
              loop.nextitem|default('x') }}|
          {%- endfor %}"""
      )
      output = tmpl.render(seq=list(range(4)))
      assert output == "x-0-1|0-1-2|1-2-3|2-3-x|"
  
imports: import asyncio
  import pytest
  from jinja2 import DictLoader
  from jinja2 import Environment
  from jinja2 import Template
  from jinja2.asyncsupport import auto_aiter
  from jinja2.exceptions import TemplateNotFound
  from jinja2.exceptions import TemplatesNotFound
  from jinja2.exceptions import UndefinedError
label_desc: Use image node_id 6 for calling the TestAsyncForLoop obj's underlying member method code with example usage: obj.test_lookaround(test_env_async) without return types