@Override
  public boolean caresAbout(Expression.PartialInput input) {
    return sourceElementProcessors.stream().anyMatch(e -> e.expression()
      .partialEvaluate(input)
      .simplify() != Expression.FALSE);
  }
Call {@code handler} for different events based on which interfaces {@code handler} implements:
{@link OsmRelationPreprocessor}, {@link FinishHandler}, {@link TilePostProcessor} or {@link LayerPostProcessor}.
planetiler-core/src/main/java/com/onthegomap/planetiler/ForwardingProfile.java