Saxon » SaxonC

I am trying to figure a way how to use and call an XPath function from Python with Saxon 11.1. The Python API shows a function get_system_function at https://www.saxonica.com/saxon-c/doc11/html/saxonc.html#PyXdmFunctionItem without showing the possible arguments. It is also not clear whether it is supposed to be static (as the correspondent C++ method seems to be) or an instance method.

I have tried to call it/access it directly as PyXdmFunctionItem.get_system_function, but that fails with "TypeError: descriptor 'get_system_function' for 'saxonc.PyXdmFunctionItem' objects doesn't apply to a 'saxonc.PySaxonProcessor' object"; trying to call it as PyXdmFunctionItem().get_system_function fails in the Cython code:

from saxonc import *

with PySaxonProcessor(license=True) as proc:
    print("Test SaxonC on Python")
    print(proc.version)
    
    parse_json = PyXdmFunctionItem().get_system_function(proc, '{http://www.w3.org/2005/xpath-functions}parse-json', 1)
    
    xdmItem = parse_json.call(proc, [proc.make_string_value('[1,2,3]')])

gives

Traceback (most recent call last):
  File "C:\Users\marti\OneDrive\Documents\xslt\blog-xslt-3-by-example\saxonc-11.1-python\json-processing\parse-json-test1.py", line 7, in <module>
    parse_json = PyXdmFunctionItem().get_system_function(proc, '{http://www.w3.org/2005/xpath-functions}parse-json', 1)
  File "saxonc.pyx", line 3968, in saxonc.PyXdmFunctionItem.get_system_function
    c_func = self.derivedfptr.getSystemFunction(proc.thisptr, name, arity)
TypeError: expected bytes, str found