API for writing statistics to both sharded records and binary pb.

This PTransform assumes that input represents sharded statistics, which are written directly. These statistics are also merged and written to a binary proto.

Currently Experimental.

binary_proto_path Output path for writing statistics as a binary proto.
records_path_prefix File pattern for writing statistics to sharded records.
columnar_path_prefix Optional file pattern for writing statistics to columnar outputs. If provided, columnar outputs will be written when supported.

pipeline None