i wanted to update my exsiting subnet in Terraform, firstly i did this command

```
terraform import 'azurerm_subnet.example' /subscriptions/id-id-id-id/resourceGroups/tfeastus/providers/Microsoft.Network/virtualNetworks/myVnetTF/subnets/SUBNET-0

```

the import was successfull, so i made my terraform template

```
terraform {
  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "~>2.0"
    }
  }
}
provider "azurerm" {
  features {}
}
variable "vnetName" {
  type = string
}
variable "location" {
  type = string
}
variable "resource_group_name" {
  type = string
}
variable "subnetName" {
  type = string
}
data "azurerm_virtual_network" "vnet" {
  name                = var.vnetName
  location            = var.location
  resource_group_name = var.resource_group_name

}
resource "azurerm_subnet" "example" {
  name                 = var.subnetName
  resource_group_name  = var.resource_group_name
  virtual_network_name = var.vnetName

  delegation {
    name = "delegation"
    service_delegation {
      name = "Microsoft.Web/serverFarms"
    }
  }
}

```

Although, after terraform apply i get an error saying that `│ "address_prefix": one of` address\_prefix,address\_prefixes `must be specified`. If i already imported the subnet, and it is in the `terraform.tfstate` why do i have to provide an already existing address\_prefix?