code: def _verify_r():
      if not util.which("Rscript"):
          raise REnvError(
              "R is not installed on this system. Refer to "
              "https://www.r-project.org/ for details."
          )
  
file_path: guildai/guild/plugins/r_util.py
imports: import os
  import re
  import subprocess
  from guild import util
label_desc: Use image node_id 3 for calling a global function with example usage: _verify_r() without return types