title: Add Environment variables while creating a Google Compute Engine VM Instance
body: <p>I'm creating a VM instance through cloud function in GCE.I want to add some environment variables to the Instance during creation.
  I'm referring this code for instance creation:</p>
  
  <p><a href="https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/compute/api/create_instance.py" rel="nofollow noreferrer">https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/compute/api/create_instance.py</a></p>
  
  <p>I don't want to add this in startup script, because already I'm running a set of tasks in startup script, and i want one of those tasks to use these environment variables. Is there any other way,like passing values in config, while creating instance ?</p>