problem with validation when `extends` key is used

[surajnarwade]

main docker-compose file is:

version: '2'

services:
  test_micro_service_api:
    extends :
      file : ../v-test/docker-compose-test.yml
      service : v_test

child docker-compose file is:

version: "2"

services:
  v_test:
    build:
      context: .
      dockerfile: ./Dockerfile
    env_file:
     - ../locale/env/test_service
    environment:
     DEBUG: 'true'
    command: bash -c "python ./manage.py migrate && python ./manage.py runserver 0.0.0.0:8018"
    volumes:
     - .:/v-test
    ports:
     - "8018:8018"

error is:

$ libcompose up
WARN[0000] Note: This is an experimental alternate implementation of the Compose CLI (https://github.com/docker/compose) 
ERRO[0000] Failed to parse service test_micro_service_api: Service 'v_test' configuration key 'build' contains an invalid type, it should be a string. 
ERRO[0000] Could not parse config for project tmp : Service 'v_test' configuration key 'build' contains an invalid type, it should be a string. 
FATA[0000] Failed to read project: Service 'v_test' configuration key 'build' contains an invalid type, it should be a string.