i wanted to add the updated version ( FCM APIs to HTTP v1 ) of fcm  api which is like this 

headers = {
    "Authorization": "Bearer " + _get_access_token(),
    "Content-Type": "application/json; UTF-8"
}
response = requests.post(
    "https://fcm.googleapis.com/v1/projects/my_project_id/messages:send",
    data=json.dumps(message),
    headers=headers

here is code which i have included to get the access token 

def _get_access_token():
  """Retrieve a valid access token that can be used to authorize requests.
:return: Access token.
  """
  credentials = service_account.Credentials.from_service_account_file(
    'service_account_key.json', scopes=SCOPES)
  request = google.auth.transport.requests.Request()
  credentials.refresh(request)
  return credentials.token

print(_get_access_token())

 I have added the service account json to same directory 

service_account_key.json

 directory look like this 

module
|-- models
|   |-- service_account_key.json
|-- |---get_token_from_key.py
|   |-- __init__.py
|-- other_module_files..

 i,m getting this error 

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/odoo/modules/_service_account_info.py", line 78, in from_filename
    with io.open(filename, "r", encoding="utf-8") as json_file:
FileNotFoundError: [Errno 2] No such file or directory: 'service_account_key.json'