code: def parse_xhtml_reaction_notes(entry):
      
      properties = {}
      if entry.xml_notes is not None:
          cobra_notes = dict(parse_xhtml_notes(entry))
  
          if 'subsystem' in cobra_notes:
              properties['subsystem'] = cobra_notes['subsystem']
  
          if 'gene_association' in cobra_notes:
              properties['genes'] = cobra_notes['gene_association']
  
          if 'ec_number' in cobra_notes:
              properties['ec'] = cobra_notes['ec_number']
  
          if 'authors' in cobra_notes:
              properties['authors'] = [
                  a.strip() for a in cobra_notes['authors'].split(';')]
  
          if 'confidence' in cobra_notes:
              try:
                  value = int(cobra_notes['confidence'])
              except ValueError:
                  logger.warning(
                      'Unable to parse confidence level for {} as an'
                      ' integer: {}'.format(
                          entry.id, cobra_notes['confidence']))
                  value = cobra_notes['confidence']
              properties['confidence'] = value
  
      return properties
docs: Return reaction properties defined in the XHTML notes.
  
      Older SBML models often define additional properties in the XHTML notes
      section because structured methods for defining properties had not been
      developed. This will try to parse the following properties: ``SUBSYSTEM``,
      ``GENE ASSOCIATION``, ``EC NUMBER``, ``AUTHORS``, ``CONFIDENCE``.
  
      Args:
          entry: :class:`SBMLReactionEntry`.