def get_synsets(lemma, synset_dict):
    """Return synonym set given a word lemma.

    The function requires that the synset_dict is passed into it. In our case
    we provide downloadable models from MCR (Multilingual-Central-Repository).
    :cite:`gonzalez2012multilingual`. If the lemma is not found in the
    synset_dict, then this function returns a set with the lemma in it.

    :param lemma: Lemma to be look-up into the synset
    :type lemma: string
    :param synset_dict: key-value pairs, lemma to synset
    :type synset_dict: Python dict
    :return: The set of synonyms of a given lemma
    :rtype: Python set of strings
    """
    return synset_dict.get(lemma, {lemma})