code: def test_get_from_envfile():
      ETC_OS_RELEASE = "/etc/os-release"
      with tempfile.TemporaryFile() as f:
          xtr = SupportMatrixExtractor("x", "22.02", f.name)
          xtr.get_from_envfile(ETC_OS_RELEASE, "PRETTY_NAME")
          assert (
              xtr.data["x"]["22.02"].get("PRETTY_NAME")
              == "Debian GNU/Linux 10 (buster)"
          )
  
          xtr.get_from_envfile(ETC_OS_RELEASE, "PRETTY_NAME", "os")
          assert (
              xtr.data["x"]["22.02"].get("os")
              == "Debian GNU/Linux 10 (buster)"
          )
  
          xtr.get_from_envfile(ETC_OS_RELEASE, "BAZ")
          assert (
              xtr.data["x"]["22.02"].get("BAZ")
              == SupportMatrixExtractor.ERROR
          )
  
file_path: Merlin/docs/test_extractor.py
imports: import json
  import os
  import shutil
  import tempfile
  from pathlib import Path
  from extractor import SupportMatrixExtractor
label_desc: Use image node_id 1 for calling a global function with example usage: test_get_from_envfile() without return types