def kmerize_contig(contig, kmer_size):
    """Return generator of kmers in contig

    The returned kmers are not lexicographically lowest.

    >>> list(kmerize_contig('ATTT', 3))
    ['ATT', 'TTT']
    """
    assert len(contig) >= kmer_size
    for start in range(len(contig) - kmer_size + 1):
        yield contig[start:start + kmer_size]
