code: func (ix *Index) updateDeletesCache(deleteClaim schema.Claim) error {
  	target := deleteClaim.Target()
  	deleter := deleteClaim.Blob()
  	when, err := deleter.ClaimDate()
  	if err != nil {
  		return fmt.Errorf("Could not get date of delete claim %v: %v", deleteClaim, err)
  	}
  	targetDeletions := append(ix.deletes.m[target],
  		deletion{
  			deleter: deleter.BlobRef(),
  			when:    when,
  		})
  	sort.Sort(sort.Reverse(byDeletionDate(targetDeletions)))
  	ix.deletes.m[target] = targetDeletions
  	return nil
  }
docs: // updateDeletesCache updates the index deletes cache with the cl delete claim.
  // deleteClaim is trusted to be a valid delete Claim.