Embedded Python: How to Compile Script from Memory (Not a File) That Requires "Pickle" - python-3.x

Question

My app hosts embedded Python so that users can create and run scripts using the Python 3.9 framework for macOS. The scripts are not stored as files on disk, but in the my app's memory.
In general, I am successfully compiling and running these scripts from memory using Py_CompileString/PyImport_ExecCodeModule
However, I get a "pickle" error when attempting to run a script that uses the multiprocessing module.
I created a command line program to replicate the problem. Upon trying to execute the following code as a string (with proper newlines, etc.) using PyRun_SimpleString()
from multiprocessing import Process
import sys
def foo(name):
print('executing foo', name)
def python_main():
# set the executable to path to python, not this command line program
sys.executable = '/Library/Frameworks/Python.framework/Versions/3.9/Resources/Python.app/Contents/MacOS/Python'
# set sys.argv[0] to '__main__' since it will be empty otherwise
sys.argv[0] = '__main__'
print('creating process')
p = Process(target=foo, args=('Hi Bob!',))
p.start()
p.join()
print('process complete - exit code', p.exitcode)
if __name__ == '__main__':
python_main()
I receive the following output:
creating process
starting process
joining process
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/spawn.py", line 116, in spawn_main
exitcode = _main(fd, parent_sentinel)
File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/spawn.py", line 126, in _main
self = reduction.pickle.load(from_parent)
AttributeError: Cant get attribute 'foo' on <module '__main__' (built-in)>
process complete - exit code 1
python_main complete
If I run the same code from an actual file called mp.py as follows, then it executes successfully.
PyRun_SimpleString("import mp; mp.python_main()");
Is there something I must do to allow my in-memory script to be pickled as it is when the file is on disk?
P.S. It is worth mention that when I compile the code using Py_CompileString/PyImport_ExecCodeModule, the code looks something like this:
codeObj = Py_CompileString(inScript.c_str(), "mp.py", Py_file_input);
moduleObj = PyImport_ExecCodeModule("mp", codeObj);
so the code does have an "imginary" file name (imaginary because the script text is in memory, not on disk) and a real module name.