def parse_string
      direction = clause.split[1]
      field = clause.split[0]
      direction = "asc" unless %w(asc desc).include?(direction)
      ["$order_by", ["$#{direction}", field]]
    end
def parse_string
      direction = clause.split[1]
      field = clause.split[0]
      direction = "asc" unless %w(asc desc).include?(direction)
      ["$order_by", ["$#{direction}", field]]
    end
Parses a string clause, defaults direction to asc if missing or invalid

 * *Returns* :
   - A ReQON formatted array
 * *Examples* :
    @clause = "happy_trees desc"
    @clause.parse
    => ["$order_by", ["$desc", "happy_trees"]]