-import com.google.common.base.Preconditions;
-import java.util.Collection;
-import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidate;
+import static java.util.Objects.requireNonNull;
+
+import java.util.List;
+import org.opendaylight.yangtools.yang.data.tree.api.DataTreeCandidate;