code: def activate():
      
  
      parent = lib.parent()
  
      try:
          cmd = lib.cmd(parent)
      except SystemError as exc:
          lib.echo(exc)
          sys.exit(lib.PROGRAM_ERROR)
  
      # Store reference to calling shell
      context = lib.context(root=_extern.cwd())
      context["BE_SHELL"] = parent
  
      if lib.platform() == "unix":
          context["BE_TABCOMPLETION"] = os.path.join(
              os.path.dirname(__file__), "_autocomplete.sh").replace("\\", "/")
  
      context.pop("BE_ACTIVE", None)
  
      sys.exit(subprocess.call(cmd, env=context))
docs: Enter into an environment with support for tab-completion
  
      This command drops you into a subshell, similar to the one
      generated via `be in ...`, except no topic is present and
      instead it enables tab-completion for supported shells.
  
      See documentation for further information.
      https://github.com/mottosso/be/wiki/cli