docs: private void initHeader(final List<String> currentFields) {
  		final Map<String, Integer> localHeaderMap = new LinkedHashMap<>(currentFields.size());
  		for (int i = 0; i < currentFields.size(); i++) {
  			final String field = currentFields.get(i);
  			if (StrUtil.isNotEmpty(field) && false ==localHeaderMap.containsKey(field)) {
  				localHeaderMap.put(field, i);
  			}
  		}
  		
  		header = new CsvRow(this.lineNo, Collections.unmodifiableMap(localHeaderMap),  Collections.unmodifiableList(currentFields));
  	}