def export_corpus(corpus, outfolder, context_type='document'):
    """
    Converts a vsm.corpus.Corpus object into a Weka-compatible `ARFF file`_.

    :param corpus: VSM Corpus object to convert to lda-c file
    :type corpus: vsm.corpus.Corpus

    :param outfolder: Directory to output "vocab.txt" and "corpus.dat"
    :type string: path

    .. _ARFF file: https://weka.wikispaces.com/ARFF
    """
    pass
