code: func (s *Snapshot) inturn(number uint64, signer common.Address) bool {
  	signers, offset := s.signers(), 0
  	for offset < len(signers) && signers[offset] != signer {
  		offset++
  	}
  	return (number % uint64(len(signers))) == uint64(offset)
  }
docs: // inturn returns if a signer at a given block height is in-turn or not.