docs: def setup(self, app):
          """Parse and prepare the plugin's configuration."""
          super().setup(app)
  
          self.enabled = len(self.cfg.backends)
  
          self.default = self.cfg.default
          if not self.default and self.enabled:
              self.default = self.cfg.backends[0][0]
  
          self.backends_hash = {name: parse.urlparse(loc) for (name, loc) in self.cfg.backends}
          if self.default and self.default not in self.backends_hash:
              raise PluginException('Backend not found: %s' % self.default)