Nest groups from CSV - powershell

Question

for hours now I'm searching the web but didn't find a suitable solution yet.
I want to add groups as member to other groups and have a CSV as source.
The CSV looks like (first line is the header)...
agroup,bgroup1,bgroup2,bgroup3,...
a-group1,b-group1,b-group2,b-group3
a-group2,b-group5
a-group3,b-group2,b-group3,b-group4,b-group5,b-group6
a-group4,b-group15,b-group23
(...and so forth... Where a-group should represent company roles and b-group corresponding permissions to ressources but that is not the point of this question)
So, following this example a-group1 has b-group1, b-group2 and b-group3 as members.
Now my problem is that I don't know how to iterate through columns 2 to end and ignore empty columns/values.
Other questions here on stackoverflow are about CSV with neatly user,group but I can't do this because the CSV covers hundrets of rows and columns.
Someone please help.
Edit
Sorry, forgot my code so far.
Import-Module ActiveDirectory
$path = Split-Path -parent $MyInvocation.MyCommand.Definition
$newpath = $path + "\input.csv"
$csv = #()
$csv = Import-Csv -Path $newpath -Delimiter ";"
$csv | Foreach-Object {
foreach ($property in $_.PSObject.Properties) {
Write-Host $_.agroup $property.Value
}
}
I did a write-host for testing.
Final Edit
Working code:
$csv | Foreach-Object {
foreach ($property in $_.PSObject.Properties) {
if ($property.Value -ne $null -and $property.Value -ne "") {
Add-ADGroupMember -Identity $_.agroup -Member $property.Value -WhatIf }
}
}

Answer 1

With this code I filtered out the empty values. You might want to remove whatif to have it working.
$csv | Foreach-Object {
foreach ($property in $_.PSObject.Properties) {
if ($property.Value -ne $null -and $property.Value -ne "") {
Add-ADGroupMember -Identity $_.agroup -Member $property.Value -WhatIf }
}
}