public static <T_ROW, T_VAL1> Function<T_ROW, String> toStringFunc(
            final Function<T_ROW, T_VAL1> valueExtractor1,
            final Function<T_VAL1, Object> valueExtractor2) {
        return (T_ROW row) ->
                NullSafe.toStringOrElse(row, valueExtractor1, valueExtractor2, "");
    }
Returns a {@link Function} that will call the toString method on the value returned
from passing the row through valueExtractor1 then valueExtractor2. If any intermediate value
is null, the returned function will return an empty string.
stroom-core-client/src/main/java/stroom/util/client/DataGridUtil.java