def mexists(keys)
      validate_key_array(keys)

      Result.new {
        existing_keys = GitHub::SQL.values(<<-SQL, :keys => keys, :connection => connection).to_set
          SELECT `key` FROM key_values WHERE `key` IN :keys AND (`expires_at` IS NULL OR `expires_at` > NOW())
        SQL

        keys.map { |key| existing_keys.include?(key) }
      }
    end
def mexists(keys)
      validate_key_array(keys)

      Result.new {
        existing_keys = GitHub::SQL.values(<<-SQL, :keys => keys, :connection => connection).to_set
          SELECT `key` FROM key_values WHERE `key` IN :keys AND (`expires_at` IS NULL OR `expires_at` > NOW())
        SQL

        keys.map { |key| existing_keys.include?(key) }
      }
    end
mexists :: [String] -> Result<[Boolean]>

 Checks for existence of all specified keys. Booleans will be returned in
 the same order as keys are specified.

 Example:

   kv.mexists(["foo", "octocat"])
     # => #<Result value: [true, false]>