code: def platform():
      
      executable = parent()
      basename = os.path.basename(executable)
      basename, _ = os.path.splitext(basename)
  
      if basename in ("bash", "sh"):
          return "unix"
      if basename in ("cmd", "powershell"):
          return "windows"
  
      raise SystemError("Unsupported shell: %s" % basename)
docs: Return platform for the current shell, e.g. windows or unix