text: import base64
  import json
  import time
  
  from google.appengine.api import app_identity
  
  DEFAULT_SERVICE_ACCOUNT = app_identity.get_service_account_name()
  
  
  def generate_jwt():
      """Generates a signed JSON Web Token using the Google App Engine default
      service account."""
      now = int(time.time())
  
      header_json = json.dumps({
          "typ": "JWT",
          "alg": "RS256"
      })
  
      payload_json = json.dumps({
          'iat': now,
          "exp": now + 3600,
          'iss': DEFAULT_SERVICE_ACCOUNT,
          'sub': DEFAULT_SERVICE_ACCOUNT,
          'aud': 'ingestion_pipeline',
          "email": DEFAULT_SERVICE_ACCOUNT
      })
  
      headerAndPayload = '{}.{}'.format(base64.urlsafe_b64encode(header_json), base64.urlsafe_b64encode(payload_json))
      (key_name, signature) = app_identity.sign_blob(headerAndPayload)
      signed_jwt = '{}.{}'.format(headerAndPayload, base64.urlsafe_b64encode(signature))
  
      return signed_jwt
  