public ColumnMetadata primaryColumnMetadata() {
    return Objects.requireNonNull(columns.get(primaryColumn),
      "No geoparquet metadata for primary column " + primaryColumn);
  }
Returns the geoarrow type string of this geometry column, or null if not geoarrow.
planetiler-core/src/main/java/com/onthegomap/planetiler/reader/parquet/GeoParquetMetadata.java