code: def is_zonefile_cached( zonefile_hash, zonefile_dir, validate=False):
      
      zonefile_path = atlas_zonefile_path(zonefile_dir, zonefile_hash)
      zonefile_path_legacy = atlas_zonefile_path_legacy(zonefile_dir, zonefile_hash)
  
      res = False
      for zfp in [zonefile_path, zonefile_path_legacy]:
          
          if not os.path.exists(zfp):
              continue
  
          if validate:
              data = _read_atlas_zonefile(zfp, zonefile_hash)
              if data:
                  # yup!
                  res = True
                  break
  
          else:
              res = True
              break
  
      return res
docs: Do we have the cached zonefile?  It's okay if it's a non-standard zonefile.
      if @validate is true, then check that the data in zonefile_dir_path/zonefile.txt matches zonefile_hash
  
      Return True if so
      Return False if not