code: function(key, regex, modifiers) {
          this._addCondition(key, '$regex', regex);
          if (!modifiers) {
            modifiers = '';
          }
          // Javascript regex options support mig as inline options but store them
          // as properties of the object. We support mi & should migrate them to
          // modifiers
          if (regex.ignoreCase) {
            modifiers += 'i';
          }
          if (regex.multiline) {
            modifiers += 'm';
          }
  
          if (modifiers && modifiers.length) {
            this._addCondition(key, '$options', modifiers);
          }
          return this;
        }
docs: Add a regular expression constraint for finding string values that match
  the provided regular expression.
  This may be slow for large datasets.
  @param {String} key The key that the string to match is stored in.
  @param {RegExp} regex The regular expression pattern to match.
  @return {AV.Query} Returns the query, so you can chain this call.