code: func partialVerify(certs []*x509.Certificate) bool {
  	n := len(certs)
  	if n == 0 {
  		return false
  	}
  	for i := 0; i < n-1; i++ {
  		if certs[i].CheckSignatureFrom(certs[i+1]) != nil {
  			return false
  		}
  	}
  	return true
  }
docs: // Check if the certs form a partial cert chain: every cert verifies
  // the signature of the one in front of it.