docs: private EREFiller toFiller(final Element xml, final String docid) {
      final String id = generateID(XMLUtils.requiredAttribute(xml, "id"), docid);
      final String type = XMLUtils.requiredAttribute(xml, "type");
      final int extentStart = XMLUtils.requiredIntegerAttribute(xml, "offset");
      final int extentEnd = extentStart + XMLUtils.requiredIntegerAttribute(xml, "length") - 1;
      final String text = xml.getTextContent();
  
      final ERESpan span = ERESpan.from(extentStart, extentEnd, text);
  
      final EREFiller ereFiller;
      if (xml.hasAttribute(NORMALIZED_TIME_ATTR)) {
       ereFiller = EREFiller.fromTime(id, type, xml.getAttribute(NORMALIZED_TIME_ATTR), span);
      } else {
        ereFiller = EREFiller.from(id, type, span);
      }
      idMap.put(id, ereFiller);
      return ereFiller;
    }