Services.mssqlserver.networks contains an invalid type, it should be an array, or an object

Hi All,
I am trying to run a docker image through docker compose in my visual studio and getting below error:
services.mssqlserver.networks contains an invalid type, it should be an array, or an object.
Can anybody help me on this. Here is my Yaml file:

version: ‘3.4’

networks:
frontend:
backend:

services:
catalog:
image: jewels/catalogapi
build:
context: .\ProductCatelogApi
dockerfile: Dockerfile
environment:
DatabaseServer: mssqlserver
DatabaseName: CatalogDb
DatabaseUser: sa
DatabasePassword: ProductApi(!)
ExternalCatalogBaseUrl: http://localhost:6800
ports:
- “6800:80”
container_name: jewelscatalogapi
networks:
- backend
- frontend
depends_on:
- mssqlserver

mssqlserver:
image: “microsoft/mssql-server-linux:latest”
environment:
ACCEPT_EULA: Y
SA_PASSWORD: ProductApi(!)
ports:
- “1448:1433”
container_name: jewelssqlserver
networks:
-backend