code: def get_shortname(self):
          
          disqus_shortname = self.state.document.settings.env.config.disqus_shortname
          if not disqus_shortname:
              raise ExtensionError('disqus_shortname config value must be set for the disqus extension to work.')
          if not RE_SHORTNAME.match(disqus_shortname):
              raise ExtensionError('disqus_shortname config value must be 3-50 letters, numbers, and hyphens only.')
          return disqus_shortname
docs: Validate and returns disqus_shortname config value.
  
          :returns: disqus_shortname config value.
          :rtype: str