https://beam.apache.org/contribute/ptransform-style-guide/ is a collection of best practices for developing PTransform's.
Some of these practices shaped up relatively recently, and some Beam transforms violate them, introducing inconsistency into Beam APIs and tempting new library writers and users into mimicking code that's best not mimicked.
This is an umbrella bug for cleanups bringing individual Beam transforms in accordance with the style guide.
Please file 1 bug per transform that needs to be fixed (e.g. "Bring KafkaIO in accordance with style guide"); in the bug, describe which aspects need to be fixed (e.g. "should use AutoValue; should explicitly specify type parameters; should not use Coders for serialization") and link it with the current bug.