code: public BioCDocument readDocument()
        throws XMLStreamException {
  
      if (reader.document != null) {
        BioCDocument thisDocument = reader.document;
        reader.read();
        return thisDocument;
      } else {
        return null;
      }
    }
docs: Reads one BioC document from the XML file.
  
  @return the BioC document
  @throws XMLStreamException if an unexpected processing error occurs