message: Deprecate getPrimitive that takes a proto key as input.
  This method package-protected and is not used, except in some tests. It seems more logical to always use the public method that takes the output prefix as input.
diff: @@ -24,6 +24,7 @@ import com.google.crypto.tink.proto.Keyset;
  import com.google.crypto.tink.proto.OutputPrefixType;
  import com.google.crypto.tink.subtle.Hex;
  import com.google.errorprone.annotations.CanIgnoreReturnValue;
  +import com.google.errorprone.annotations.InlineMe;
  import java.security.GeneralSecurityException;
  import java.util.ArrayList;
  import java.util.Arrays;
  @@ -194,6 +195,10 @@ public final class PrimitiveSet<P> {
  }
  /** Returns the entries with primitives identified by the ciphertext prefix of {@code key}. */
  + @InlineMe(
  + replacement = "this.getPrimitive(CryptoFormat.getOutputPrefix(key))",
  + imports = {"com.google.crypto.tink.CryptoFormat"})
  + @Deprecated
  List<Entry<P>> getPrimitive(Keyset.Key key) throws GeneralSecurityException {
  return getPrimitive(CryptoFormat.getOutputPrefix(key));
  }
  