Currently, the framework is lagging unit testing. Add some unit test.

When the user runs gmailctl init the gmailctl.libsonnet is created. Unfortunately the file it never updated automatically again.
I propose gmailctl init --reset-lib or similar flag to force update all library files (current and future).
It is understandable that gmailctl will not rewrite config.jsonnet as it may contain user configuration, however library files are not expected to be t

The label distribution in the description for continuous labels should match pandas describe.