transforer获取源表列名

在自定义transformer时，怎么通过record获取源表的列名呢，或者通过其他方法可以获取到呢

Start by tracing the custom transformer API and the Record object referenced in the issue, then check whether source-table column metadata is exposed anywhere. No source file or test is named, so confirm the intended behavior with the existing transformer documentation or examples; done means documenting a supported way to obtain the source column names, or clearly recording that it is unavailable.

Written by the indexing model from the issue text.