boolean onlyField(String name) {
      return !type.isPrimitive() && fieldCount == 1 &&
        type.asGroupType().getFieldName(0).equalsIgnoreCase(name);
    }
Returns a new context that flattens-out this level of the hierarchy and writes values into the parent field.
planetiler-core/src/main/java/com/onthegomap/planetiler/reader/parquet/ParquetRecordConverter.java