@Override
    public Object apply(String key) {
      if (key != null) {
        return switch (key) {
          case MATCH_KEY -> wrapNullable(matchKey());
          case MATCH_VALUE -> wrapNullable(matchValue());
          default -> parent.apply(key);
        };
      } else {
        return null;
      }
    }
Context available after a feature has been matched.
<p>
Adds {@code match_key} and {@code match_value} variables that capture which tag key/value caused the feature to be
included.

@param parent    The parent context
@param matchKeys Keys that triggered the match
planetiler-custommap/src/main/java/com/onthegomap/planetiler/custommap/Contexts.java