Provisioning Teams in GitHub using Terraform - team hierarchy - terraform

Question

I am attempting to use the github terraform provider to simplify how we manage teams in our GitHub Organization. To reduce the amount of changes to the Terraform code I wanted to use a solution like https://learn.hashicorp.com/tutorials/terraform/github-user-teams where contributors would only need to change values in a csv file.
The example does not include a solution for having teams be members of teams. Looking at the provider documentation https://registry.terraform.io/providers/integrations/github/latest/docs/resources/team, it requires parent_team_id be provided.
My current approach is to have two CSV files, one with parent team name and one without, and build a local mapping. The issue is that when I apply I get the error
The "for_each" value depends on resource attributes that cannot be determined
until apply, so Terraform cannot predict how many instances will be created.
To work around this, use the -target argument to first apply only the
resources that the for_each depends on.
Can someone point out where I am going wrong, it will be something simple but I cannot see what.
NOTE: I am aware (after posting) that I am not actually using the parent_team_id in the second team resource, thats a simple fix once I get the local working.
Resources
resource "github_team" "l0" {
for_each = {
for team in csvdecode(file("teams.csv")) :
team.name => team
}
name = each.value.name
description = each.value.description
privacy = each.value.privacy
create_default_maintainer = true
}
resource "github_team" "l1" {
for_each = {
for team in local.l1_mapping : team.name => team
}
name = each.value.name
description = each.value.description
privacy = each.value.privacy
create_default_maintainer = true
depends_on = [
github_team.l0
]
}
Locals
# Create local values to retrieve items from CSVs
locals {
l1_team_plus = {
for file2 in csvdecode(file("l1_teams.csv")) :
file2.name => file2
}
l1_mapping = flatten([
for team2 in local.l1_team_plus : [
for t in github_team.l0 : {
id = t.id
slug = t.slug
team2 = team2
} if t.slug == team2.name
]
])
}