docs: function (oe) {
              var s = string.format("%s %s", this.literal(oe.expression), oe.descending ? "DESC" : "ASC");
              if (oe.nulls) {
                  s = string.format("%s NULLS %s", s, oe.nulls === "first" ? "FIRST" : "LAST");
              }
              return s;
          }