How to invoke a function defined in another Powershell script within a Workflow?

Question

Usually, I use dot-sourcing to "import" my function defined in other script files.

But the Powershell Workflow does not allow dot-sourcing, and it can't recognize functions defined out of scope.

Is there any possible way instead of copy-pasting all the functions into the Workflow to invoke them?

For example:

# another_script.ps1

function FuncToBeCall {
  # do something
}

# main.ps1

# Usual way I import the functions
. $PSScriptRoot\another.script.ps1

# I can invoke function here normally
FuncToBeCall

Workflow RunSomething
{

  # do something...

  # Want to invoke here, or in InlineScript/Sequence/Parallel
  FuncToBeCall

}

RunSomething

PS. The reason I try to do it in the Workflow way is to take advantage of the Parallel. Otherwise, I might do this in a normal way. Just looking for the best practice.