Merge pull request #3260 from nathanielmanistaatgoogle/protocol-objects

src/python/grpcio/grpc/_links/service.py

src/python/grpcio/grpc/framework/core/_ingestion.py

src/python/grpcio/grpc/framework/core/_interfaces.py

src/python/grpcio/grpc/framework/core/_operation.py

src/python/grpcio/grpc/framework/core/_protocol.py

src/python/grpcio/grpc/framework/core/_reception.py

src/python/grpcio/grpc/framework/crust/_calls.py

src/python/grpcio/grpc/framework/crust/_control.py

src/python/grpcio/grpc/framework/crust/_service.py

src/python/grpcio/grpc/framework/interfaces/base/base.py

...python/grpcio/grpc/framework/interfaces/base/utilities.py

...io_test/grpc_test/framework/interfaces/base/test_cases.py