public static PartialInput ofSource(String source) {
      return new PartialInput(Set.of(source), Set.of(), Map.of(), Set.of());
    }
Partial attributes of a set of features that are known ahead of time, for example a hive-partitioned parquet input
file.
<p>
Features within this set will only add tags but not change them, and the source/layer/geometry type will be one of
the values specified in those sets. If the set is empty, the values are not known ahead of time.
planetiler-core/src/main/java/com/onthegomap/planetiler/expression/Expression.java