Serverless Negs Backends don't work as expected

TL;DR

In this code block, it must be lookup(each.value, "description", null) instead of lookup(backend.value, "description", null) !?! The fact that backend.value doesn't make any sense in this context I believe !!

Expected behavior

Use each.value instead of backend.value in the code block dynamic "backend" { ... } of the resource "google_compute_backend_service" in the main.tf.

Observed behavior

No response

Terraform Configuration

dynamic "backend" {
    for_each = toset(each.value["groups"])
    content {
      description = lookup(backend.value, "description", null)
      group       = lookup(backend.value, "group")

    }
}

Terraform Version

terraform {
  required_version = ">= 1.3"
  required_providers {

    google = {
      source  = "hashicorp/google"
      version = ">= 4.50, < 5.0"
    }
    google-beta = {
      source  = "hashicorp/google-beta"
      version = ">= 4.50, < 5.0"
    }
    random = {
      source  = "hashicorp/random"
      version = ">= 2.1"
    }
  }

  provider_meta "google" {
    module_name = "blueprints/terraform/terraform-google-lb-http:serverless_negs/v9.1.0"
  }

  provider_meta "google-beta" {
    module_name = "blueprints/terraform/terraform-google-lb-http:serverless_negs/v9.1.0"
  }

}

Additional information