Convert HTTP query params to mongodb query syntax.

    Converts the parse query params into a mongodb spec.

    :param dict query_params: return of func:`rest.process_params`

def params_to_mongo(query_params):
    """Convert HTTP query params to mongodb query syntax.

    Converts the parse query params into a mongodb spec.

    :param dict query_params: return of func:`rest.process_params`
    """
    if not query_params:
        return {}
    for key, value in query_params.items():
        if isinstance(value, list):
            query_params[key] = {'$in': value}
    return query_params