'Decide on votes.
To return VALID there must be a clear majority that say VALID
and also agree on the previous block.
A tie on an even number of votes counts as INVALID.'

@classmethod
def decide_votes(cls, n_voters, n_valid, n_invalid):

    if ((n_invalid * 2) >= n_voters):
        return INVALID
    if ((n_valid * 2) > n_voters):
        return VALID
    return UNDECIDED
