code: def build(opt):
      dpath = os.path.join(opt["datapath"], "COCO_2017_Caption")
      version = None
  
      # check if data had been previously built
      if not build_data.built(dpath, version_string=version):
          print("[building data: " + dpath + "]")
  
          # make a clean directory if needed
          if build_data.built(dpath):
              # an older version exists, so remove these outdated files.
              build_data.remove_dir(dpath)
          build_data.make_dir(os.path.join(dpath, "annotations"))
          # Make the subfolder into which files will be unzipped
  
          # download the data.
          for downloadable_file in RESOURCES[3:]:
              downloadable_file.download_file(dpath)
  
          # mark the data as built
          build_data.mark_done(dpath, version_string=version)
  
imports: from parlai.core.build_data import DownloadableFile
  import parlai.core.build_data
  import os
label_desc: Use image node_id 2 for calling a global function with example usage: build(opt) without return types