code: def test_lang_to_langcode():
      assert "hi" == lang_to_langcode("Hindi")
      assert "hi" == lang_to_langcode("HINDI")
      assert "hi" == lang_to_langcode("hindi")
      assert "hi" == lang_to_langcode("HI")
      assert "hi" == lang_to_langcode("hi")
  
file_path: stanza/stanza/tests/common/test_constant.py
imports: import tempfile
  import pytest
  import stanza
  from stanza.models.common.constant import treebank_to_short_name, lang_to_langcode, is_right_to_left, two_to_three_letters, langlower2lcode
  from stanza.tests import *
label_desc: Use image node_id 2 for calling a global function with example usage: test_lang_to_langcode() without return types