Need help in TickScript for using the output of one pipeline into another

I am trying to use the output of one pipeline into another pipeline for my lambda expression. This is what I am doing

```
var datastream = stream
|from()
.database('database')
.measurement('measurement')
|groupBy('function')

var runningSD = datastream
|stddev('value')
.as('SD')

var difference = datastream
|difference('value')
.as('difference')
// Here I want to use the output of ruuningSD pipeline for my alert node such as
// |alert()
// .info(lambda: difference/runningSD > 0)

```
Is this possible to do in TickScript? One way I can think of is using eval node and its `keep` property but I am not sure if we can calculate running standard deviation using lambda expression in eval node.

Start with the TickScript datastream, runningSD, difference, alert, and eval nodes shown in the example, especially eval's keep property and lambda expressions. Determine whether one pipeline's standard-deviation output can be used in the other pipeline, and document the supported approach or the limitation.

Written by the indexing model from the issue text.