The following code, derived from example4_custom_functions.py errors, since the parser can't find the custom function.

    def times(value):
        return lambda array: list(map(lambda item: item * value, array))

    query = "true and times([1, 2, 3])"
    options: JsonQueryOptions = {"functions": {"times": times}}
    print(jsonquery(data, query, options))

Peeking at the code, it would seem that the custom arguments passed on the higher lever evaluation are not passed to recursive evaluations, and thus the function is not found.