def backup(server, backup_id, opts = {})
      raise(ArgumentError, "backup id must not be nil!") if backup_id.nil?
      opts[:backup_id] = backup_id
      return backups(server, opts)[0]
    end
def backup(server, backup_id, opts = {})
      raise(ArgumentError, "backup id must not be nil!") if backup_id.nil?
      opts[:backup_id] = backup_id
      return backups(server, opts)[0]
    end
Instructs barman to get information about a specific backup
 @param [String] server server name
 @param [String] backup_id id of the backup
 @param [Hash] opts options for creating a {Backup}
 @option opts [Boolean] :with_wal_files whether to include {WalFiles} in each {Backup}
 @return [Backup] a new {Backup} object
 @raise [ArgumentError] if backup_id is nil