For @google-cloud/kms, SetIamPolicy and GetIamPolicy is defined in googleapis/googleapis/google/cloud/kms/v1/cloudkms_gapic.yaml and it reroutes to google.iam.v1.IAMPolicy which is not supported by micro-generator now.

reroute_to_grpc_interface: google.iam.v1.IAMPolicy

For go, they add the rerouting methods manually to generated client code, [but in separate directory, or it will be rewritten by synthtool]. For current Typescript library, we manually create IAM client, and then mix-in IAM and KMS clients together(in synth.py).