code: function addPermission() {
    var permission = getPermission(
        mlutil.asArray.apply(null, arguments)
        );
    if (permission === null) {
      throw new Error('permissions.add() takes the role name and one or more insert|update|read|execute capabilities');
    }
    return insert('/array-node("permissions")', 'last-child', permission);
  }
docs: Specifies operations to patch the permissions of a document.
  @namespace patchBuilderPermissions
   
  Specifies a role to add to a document's permissions; takes a configuration
  object with the following named parameters or, as a shortcut,
  a role string and capabilities string or array.
  @method patchBuilderPermissions#add
  @since 1.0
  @param {string} role - the name of a role defined in the server configuration
  @param {string|string[]} capabilities - the capability or an array of
  capabilities from the insert|update|read|execute enumeration
  @returns {patchBuilder.PatchOperation} a patch operation