code: def test_lowercase_keys(self):
      header = "AUTHOR: Tarek Ziadé\nWhatever: Else"
      raw, unparsed = metadata.parse_email(header)
      assert len(raw) == 1
      assert "author" in raw
      assert len(unparsed) == 1
      assert "whatever" in unparsed
  
imports: import pathlib
  import pytest
  from packaging import metadata, requirements, specifiers, utils, version
  from packaging.metadata import ExceptionGroup
label_desc: Use image node_id 14 for calling the TestRawMetadata obj's underlying member method code with example usage: obj.test_lowercase_keys() without return types