Terraform local-exec and heredoc characters in output file

Terraform
1

Hello I have following code

resource "null_resource" "used_ips_list" {
  provisioner "local-exec" {
    command = <<-EOT
    aws_credentials=$(aws sts assume-role --role-arn arn:aws:iam::${data.aws_caller_identity.current.account_id}:role/<rolename>
    aws ec2 describe-network-interfaces --region eu-west-2 --filters "Name=subnet-id,Values=subnet-0ec649f72bb07c" --query 'NetworkInterfaces[*].PrivateIpAddress' >   ${data.template_file.subnet_a.rendered}

    EOT
  }
}

data "template_file" "subnet_a" {
  template = "${path.module}/subnet_a"
}


data "local_file" "create-endpoint" {
  filename   = data.template_file.subnet_a.rendered
  depends_on = ["null_resource.used_ips_list"]
}


locals {
  subnet_ip_list = data.local_file.create-endpoint.content
}

I am trying to get a list of used ips in aws account but I get heredoc charcters in the file/local variable. This is the format I get output in

"[\n    \"172.18.0.247\",\n    \"172.18.0.253\",\n    \"172.18.0.219\",\n    \"172.18.0.222\",\n    \"172.18.0.254\",\n    \"172.18.0.244\",\n    \"172.18.0.227\",\n    \"172.18.0.224\",\n    \"172.18.0.211\",\n    \"172.18.0.197\",\n    \"172.18.0.246\",\n    \"172.18.0.208\",\n    \"172.18.0.237\",\n    \"172.18.0.238\",\n    \"172.18.0.243\",\n    \"172.18.0.217\",\n    \"172.18.0.248\",\n    \"172.18.0.226\",\n    \"172.18.0.207\"\n]\n"

I have tried function like trim and split but I get this

subnet_a_ip_list = tolist([
  "[",
  "    \"172.18.0.247\",",
  "    \"172.18.0.253\",",
  "    \"172.18.0.219\",",
  "    \"172.18.0.222\",",
  "    \"172.18.0.254\",",
  "    \"172.18.0.244\",",
  "    \"172.18.0.227\",",
  "    \"172.18.0.224\",",
  "    \"172.18.0.211\",",
  "    \"172.18.0.197\",",
  "    \"172.18.0.246\",",
  "    \"172.18.0.208\",",
  "    \"172.18.0.237\",",
  "    \"172.18.0.238\",",
  "    \"172.18.0.243\",",
  "    \"172.18.0.217\",",
  "    \"172.18.0.248\",",
  "    \"172.18.0.226\",",
  "    \"172.18.0.207\"",
  "]",
  "",
])

or this

subnet_a_ip_list = <<EOT
[
    "172.18.0.247",
    "172.18.0.253",
    "172.18.0.219",
    "172.18.0.222",
    "172.18.0.254",
    "172.18.0.244",
    "172.18.0.227",
    "172.18.0.224",
    "172.18.0.211",
    "172.18.0.197",
    "172.18.0.246",
    "172.18.0.208",
    "172.18.0.237",
    "172.18.0.238",
    "172.18.0.243",
    "172.18.0.217",
    "172.18.0.248",
    "172.18.0.226",
    "172.18.0.207"
]

EOT

How can I get a list of ips ?

any help will be much appreciated