code: function _createFilter(res) {
      for (var i = 0; i < res.length; ++i) {
        var f = res[i]
  
        if (f instanceof RegExp)
          custfilt.push(f)
        else {
          //console.log('--- creating regex with `' + str + '`')
          try {
            f = new RegExp(f)
            custfilt.push(f)
          }
          catch (e) {
            f = null
          }
          if (!f) this.invalid('custom filter', res[i])
        }
      }
    }
docs: Creates a custom filter