def validateTsFlow[as: AS, mat: MAT, ec: EC](
                                                checkType: String,
                                                validationContext: ValidationContext,
                                                larSource: Source[LoanApplicationRegister, NotUsed],
                                                tsSource: Source[TransmittalSheet, NotUsed]) =
    for {
      lars <- runWithSeq(larSource)
      t <- runWithSeq(tsSource).map { ts =>
        val tsLar = TransmittalLar(ts.head, lars)
        val errors = checkType match {
          case "all" =>
            TsEngine.checkAll(tsLar,
              tsLar.ts.LEI,
              validationContext,
              TsValidationError)
          case "syntactical" =>
            TsEngine.checkSyntactical(tsLar,
              tsLar.ts.LEI,
              validationContext,
              TsValidationError)
          case "validity" =>
            TsEngine.checkValidity(tsLar,
              tsLar.ts.LEI,
              TsValidationError)
        }
        (ts, errors)
      }
        .map { x =>
          x._2
            .leftMap(xs => {
              addTsFieldInformation(x._1.head, xs.toList)
            })
            .toEither
        }
    } yield t