code: def test_non_repeating_fields_only_once(self, raw_field):
      data = "VaLuE"
      header_field = metadata._RAW_TO_EMAIL_MAPPING[raw_field]
      single_header = f"{header_field}: {data}"
      raw, unparsed = metadata.parse_email(single_header)
      assert not unparsed
      assert len(raw) == 1
      assert raw_field in raw
      assert raw[raw_field] == data
  
imports: import pathlib
  import pytest
  from packaging import metadata, requirements, specifiers, utils, version
  from packaging.metadata import ExceptionGroup
label_desc: Use image node_id 1 for calling the TestRawMetadata obj's underlying member method code with example usage: obj.test_non_repeating_fields_only_once(raw_field) without return types