docs: static DBaseFileAttributePool getPool(URL dbaseFile) {
  		DBaseFileAttributePool pool = null;
  		if (dbaseFile != null) {
  			if (pools == null) {
  				pools = new WeakValueTreeMap<>();
  			}
  			pool = pools.get(dbaseFile.toExternalForm());
  			if (pool == null) {
  				pool = new DBaseFileAttributePool(dbaseFile);
  				pools.put(dbaseFile.toExternalForm(), pool);
  			}
  		}
  		return pool;
  	}