code: def _sortkey(self, key='uri', language='any'):
          '''
          Provide a single sortkey for this conceptscheme.
  
          :param string key: Either `uri`, `label` or `sortlabel`.
          :param string language: The preferred language to receive the label in
              if key is `label` or `sortlabel`. This should be a valid IANA language tag.
          :rtype: :class:`str`
          '''
          if key == 'uri':
              return self.uri
          else:
              l = label(self.labels, language, key == 'sortlabel')
              return l.label.lower() if l else 'f _sortkey(self, key='uri', language='any'):
          '''
          Provide a single sortkey for this conceptscheme.
  
          :param string key: Either `uri`, `label` or `sortlabel`.
          :param string language: The preferred language to receive the label in
              if key is `label` or `sortlabel`. This should be a valid IANA language tag.
          :rtype: :class:`str`
          '''
          if key == 'uri':
              return self.uri
          else:
              l = label(self.labels, language, key == 'sortlabel')
              return l.label.lower() if l else ''
docs: Provide a single sortkey for this conceptscheme.
  
          :param string key: Either `uri`, `label` or `sortlabel`.
          :param string language: The preferred language to receive the label in
              if key is `label` or `sortlabel`. This should be a valid IANA language tag.
          :rtype: :class:`str`