docs: function _matchAllFields(fields, matchAnyRegex) {
          var regExp = regExps ? matchAnyRegex ? regExps.any : regExps.all : null;
          if (regExp) {
              for (var i = 0; i < fields.length; ++i) {
                  parentBuilder.field(fields[i]).is("$regex", regExp);
              }
          }
          return parentBuilder;
      }