code: def application_version_set(version):
      
  
      cmd = ['application-version-set']
      cmd.append(version)
      try:
          subprocess.check_call(cmd)
      except OSError:
          log("Application Version: {}".format(version))
docs: Charm authors may trigger this command from any hook to output what
      version of the application is running. This could be a package version,
      for instance postgres version 9.5. It could also be a build number or
      version control revision identifier, for instance git sha 6fb7ba68.