@Override
    public boolean add(T t) {
      return true;
    }
Returns a copy of this expression where any parts that the value is known replaced with {@link #TRUE} or
{@link #FALSE} for a set of features where {@link PartialInput} are known ahead of time (ie. a hive-partitioned
parquet input file).
planetiler-core/src/main/java/com/onthegomap/planetiler/expression/Expression.java