How to Effect Parent Scope with Cmdlet Executed in Module Function

I am trying to update the parameter completion options for some cmdlets by running a function in my module.
An example of the code that is run:

$completers = Microsoft.PowerShell.Management\Get-ChildItem -Path C:\example -Filter '*.Completer.ps1'
foreach($item in $completers)
    $message = 'Re-importing Completer: {0}' -f $item.FullName
    Microsoft.PowerShell.Utility\Write-Verbose -Message $message
    & $item.FullName

An example of the completer code:

$param_name = 'UserPrincipalName'
$cmdlets = Microsoft.PowerShell.Core\Get-Command -Module 'MSOnline' -ParameterName $param_name

$argument_completer = @{
    CommandName = $cmdlets.Name
    ParameterName = $param_name
    ScriptBlock = {
        param($command_name, $parameter_name, $word_to_complete, $command_ast, $fake_bound_parameter)

        $item_list = MSOnline\Get-MsolUser | Microsoft.PowerShell.Core\Where-Object { $PSItem.DisplayName -match $word_to_complete } | Microsoft.PowerShell.Core\ForEach-Object {
            $completion_text = $PSItem.UserPrincipalName
            $tool_tip = 'The name of users in the selected tenant.'
            $list_item_text = $PSItem.DisplayName
            $completion_result_type = [System.Management.Automation.CompletionResultType]::ParameterValue


        return $item_list

Microsoft.PowerShell.Core\Register-ArgumentCompleter @argument_completer

If I run the code myself the change occurs however when I run the function that holds the code no change occurs.

How can I get the function to update the parameter completion in the parent scope?

Use Set-Variable and specify a scope?