@staticmethod
def _make_filter_string(reqd, prefd, ontos):
    """
        TODO: expand to deal with list input

        >>> z = ZoomaClient()
        >>> z._make_filter_string("atlas,gwas","gwas","efo")
        'required:[atlas,gwas],preferred:[gwas],ontologies:[efo]'
        >>> z._make_filter_string(None,None,"none")
        'ontologies:[none]'
        """
    filters = []
    if reqd:
        filters.append('required:[{}]'.format(reqd))
    if prefd:
        filters.append('preferred:[{}]'.format(prefd))
    if ontos:
        filters.append('ontologies:[{}]'.format(ontos))
    return ','.join(filters)
