code: def validate_k8s_version(namespace):
      
      if namespace.kubernetes_version:
          k8s_release_regex = re.compile(r'^[v|V]?(\d+\.\d+\.\d+.*)$')
          found = k8s_release_regex.findall(namespace.kubernetes_version)
          if found:
              namespace.kubernetes_version = found[0]
          else:
              raise CLIError('--kubernetes-version should be the full version number, '
                             'such as "1.7.12" or "1.8.7"')
docs: Validates a string as a possible Kubernetes version. An empty string is also valid, which tells the server
      to use its default version.