def generate_source(target, source, env):
    import os
    import sys
    from importlib.util import module_from_spec, spec_from_file_location

    # allow the module to import from its current folder
    sys.path.append(os.path.dirname(source[0].abspath))
    python_spec = spec_from_file_location('source', source[0].abspath)
    python_mod = module_from_spec(python_spec)
    python_spec.loader.exec_module(python_mod)
    python_mod.generate(targets = [t.abspath for t in target])

    # restore path
    sys.path = sys.path[:-1]

    return None

pygen_builder = Builder(action = generate_source)
# env.Append(BUILDERS = {'PyGen': pygen_builder})