code: def datafind_keep_unique_backups(backup_outs, orig_outs):
      
      # NOTE: This function is not optimized and could be made considerably
      #       quicker if speed becomes in issue. With 4s frame files this might
      #       be slow, but for >1000s files I don't foresee any issue, so I keep
      #       this simple.
      return_list = FileList([])
      # We compare the LFNs to determine uniqueness
      # Is there a way to associate two paths with one LFN??
      orig_names = [f.name for f in orig_outs]
      for file in backup_outs:
          if file.name not in orig_names:
              return_list.append(file)
          else:
              index_num = orig_names.index(file.name)
              orig_out = orig_outs[index_num]
              pfns = list(file.pfns)
              # This shouldn't happen, but catch if it does
              assert(len(pfns) == 1)
              orig_out.PFN(pfns[0].url, site='notlocal')
  
      return return_list
docs: This function will take a list of backup datafind files, presumably
      obtained by querying a remote datafind server, e.g. CIT, and compares
      these against a list of original datafind files, presumably obtained by
      querying the local datafind server. Only the datafind files in the backup
      list that do not appear in the original list are returned. This allows us
      to use only files that are missing from the local cluster.
  
      Parameters
      -----------
      backup_outs : FileList
          List of datafind files from the remote datafind server.
      orig_outs : FileList
          List of datafind files from the local datafind server.
  
      Returns
      --------
      FileList
          List of datafind files in backup_outs and not in orig_outs.