# File lib/mongo_mapper/plugins/modifiers.rb, line 27
        def unset(*args)
          if args[0].is_a?(Hash)
            criteria, keys = args.shift, args
            options = keys.last.is_a?(Hash) ? keys.pop : {}
          else
            keys, ids = args.partition { |arg| arg.is_a?(Symbol) }
            options = ids.last.is_a?(Hash) ? ids.pop : {}
            criteria = {:id => ids}
          end

          criteria = criteria_hash(criteria).to_hash
          updates = keys.inject({}) { |hash, key| hash[key] = 1; hash }
          modifier_update('$unset', [criteria, updates, options])
        end