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Description
Is your feature request related to a problem? Please describe.
I often run across situations where I have either a com.google.datastore.v1.Key or com.google.datastore.v1.Entity and would like to transform it into a com.google.cloud.datastore.[Key|Entity]. There currently exists fromPb constructors within this codebase, but they are not accessible outside of the com.google.datastore namespace.
Describe the solution you'd like
Making the public.
Describe alternatives you've considered
I currently have two interop packages of my own living in com.google.datastore that re-export these methods. It works but isn't great.