def make_trigrams(texts, bigram_mod, trigram_mod):
    """Return the tri-gram models for a list of text documents.
    
    Args:
        texts: A list of text documents.
        bigram_mod: A given bi-gram model.
        trigram_mod: A given tri-gram model.

    Returns:
        A list of lists. Each list contains the tri-gram model tokens for
        a document. For example:

        [['health', 'canada', 'approves', 'astrazeneca', 'covid'],
         ['covid', 'canada', 'passport', 'certainty', 'ethicist'],
         ['coronavirus', 'variant', 'could', 'canada', 'third']]

    """
    
    return [trigram_mod[bigram_mod[doc]] for doc in texts]