code: def __verify_version_exists(self, version):
      if version not in self.get_versions():
          raise ValueError("Version " + version + " does not exist.")
  
imports: import json
  import os
  from requests.auth import HTTPBasicAuth
  import requests
label_desc: Use image node_id 8 for calling the ReadMeSession obj's underlying member method code with example usage: obj.__verify_version_exists(version) without return types