code: function options(req, opts) {
    if (!req.query) req.query = {};
  
    if (typeof opts.depth === 'number') {
      req.query.depth = opts.depth;
    }
  
    if (typeof opts.tree === 'string') {
      req.query.tree = opts.tree;
    }
  
    return opts;
  }
docs: Common options