code: function toBemjson(tree, options) {
      const transform = transformFactory(tree, options);
  
      return traverse(transform, tree);
  }
docs: Augments bemNode with custom logic
  
  @callback BjsonConverter~augmentCallback
  @param {Object} bemNode - representation of bem entity
  @returns {Object} - must return bemNode
   
  Transform `tree`, which is an MDAST node, to a Bemjson node.
  
  @param {Node} tree - MDAST tree
  @param {Object} options - transform options
  @return {Object}