docs: function(cid) {
  
      if (typeof cid !== 'string') {
        throw new VError(format('Invalid container id: "%s"', pp(cid)));
      }
  
      // Find container.
      return findContainer(cid)
      // Throw an error if a container was not found.
      .tap(function(container) {
        if (!container) {
          throw new VError(format('The container "%s" does not exist!', pp(cid)));
        }
      });
  
    }