code: public OperationFuture<List<Server>> createSnapshot(Integer expirationDays, ServerFilter serverFilter) {
          List<Server> serverList = findServers(serverFilter);
  
          return powerOperationResponse(
              serverList,
              "Create Snapshot",
              client.createSnapshot(
                  new CreateSnapshotRequest()
                      .snapshotExpirationDays(expirationDays)
                      .serverIds(ids(serverList))
              )
          );
      }
docs: Create snapshot of a single server or group of servers
  
  @param expirationDays expiration days (must be between 1 and 10)
  @param serverFilter   search servers criteria
  @return OperationFuture wrapper for BaseServerResponse list