code: function (cb) {
        files.forEach(function (file) {
          var proof = file.content;
          if (!proof) return;
          if (!proof.id) {
            errors.push(file.path + ' has no ID property.');
            return;
          }
          res[proof.id] = res[proof.id] || {};
          res[proof.id][file.type] = proof;
        });
        cb();
      }
docs: Group files by ID and set on result