code: func (pks *PublicKeySegment) HeadClaim() (*envelope.Claim, error) {
  	// The head claim is the one that is not the previous claim of any others
  outerLoop:
  	for _, c1 := range pks.Claims {
  		for _, c2 := range pks.Claims {
  			if *c2.Body.Previous == *c1.ID {
  				// Something else is newer than c1
  				continue outerLoop
  			}
  
  		}
  		// nothing is newer than c1. return it
  		return &c1, nil
  	}
  
  	return nil, ErrClaimCycleFound
  }
docs: // HeadClaim returns the most recent Claim made against this PublicKey