download secret.json
create credentials
> python create_credentials.py <email>
* copy link into browser
* give app permissions
* copy code into terminal prompt
run script
> format: python process-messages.py <mode> <gmail_query> <limit> <batch_size> -- mode=dryrun|delete|trash
* example: python process-messages.py delete "in:trash" 100 5
NOTES:
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uses python2
you can run process-messages.py multiple times after creating credentials until they exire