code: def create_jwt_token(secret, client_id):
      
      assert secret, "Missing secret key"
      assert client_id, "Missing client id"
  
      headers = {
          "typ": __type__,
          "alg": __algorithm__
      }
  
      claims = {
          'iss': client_id,
          'iat': epoch_seconds()
      }
  
      return jwt.encode(payload=claims, key=secret, headers=headers).decode()
docs: Create JWT token for GOV.UK Notify
  
      Tokens have standard header:
      {
          "typ": "JWT",
          "alg": "HS256"
      }
  
      Claims consist of:
      iss: identifier for the client
      iat: issued at in epoch seconds (UTC)
  
      :param secret: Application signing secret
      :param client_id: Identifier for the client
      :return: JWT token for this request