findBySource method
Implementation
DocumentReaderValue? findBySource(DocumentReaderTextField field, int sourceType) {
DocumentReaderValue? value;
if (sourceType == -1) {
DocumentReaderValue? mrzVal = this.findBySource(field, 3);
if (mrzVal != null) return mrzVal;
value = findBySource(field, 18);
if (value != null) return value;
var visualVal = this.findBySource(field, 17);
return visualVal != null ? visualVal : null;
} else
for (DocumentReaderValue? item in field.values)
if (item != null && item.sourceType == sourceType) return item;
return null;
}