Sign in to your BILL sandbox developer account. In response, your API session is created and a sessionId is generated. Use the sessionId in all subsequent API calls to confirm that you are in a signed in session.
If your API session is inactive or idle for 35 minutes, the session expires and you are automatically signed out.
Note: After signing in, making any subsequent call resets the 35 minutes timer. You are required to sign in again and generate a new sessionId only if the session is inactive or idle for 35 minutes.