code: def test_loop_idx():
      t = Template(TEST_IDX_TEMPLATE_STR_1)
      lst = [10]
      excepted_render = "[(len=1, revindex=1, index=1, val=10)]"
      assert excepted_render == t.render(lst=lst)
  
file_path: catboost/contrib/python/Jinja2/py3/tests/test_runtime.py
imports: import itertools
  from jinja2 import Template
  from jinja2.runtime import LoopContext
label_desc: Use image node_id 1 for calling a global function with example usage: test_loop_idx() without return types