I thought about the metadata thing but decided to exclude it for the earliest versions of textract to keep things simple. If you'd like to see it in there and have a good example of how you'd like to use metadata, please feel free to throw an issue on the issue tracker https://github.com/deanmalmgren/textract/issues/
If you have any other (better?) ways of doing this, feel free to add some comments on the issue tracker.