An example of using `inspect` module to treat code as string.

exprespy.py

import re
import math
import inspect
import textwrap

import maya.cmds as cmds
import exprespy.cmd


def rotate_driver(COUNT, IN, OUT):

    # initialization
    if not COUNT:
        from maya.api.OpenMaya import (
            MVector,
            MQuaternion,
            MEulerRotation,
        )
        from math import atan2, pi as _PI
        from math import sin, cos, tan

    # ---- snip ----------------------
    
    input_rot = MEulerRotation(IN.get(AT_ROTATE, ZERO3), IN.get(AT_ROTATE_ORDER, 0)).asQuaternion()
    OUT.rotate = input_rot


def create_node(func, name, rewrite_map):
    code = inspect.getsource(func)
    code = textwrap.dedent("".join(code.splitlines(True)[1:]))

    for src, dst in rewrite_map:
        code = re.sub(r"{}(\W)".format(src), "{}\\1".format(dst), code)

    exp_node = cmds.createNode("exprespy", name=name)
    cmds.setAttr("{}.code".format(exp_node), code, type="string")
    exprespy.cmd.setCode(exp_node, code, raw=False)

    return exp_node

menu.py

import inspect
from textwrap import dedent
import maya.cmds as cmds


def add_command_menu(menu_name, label, parent, command_func, **args):
    # type: (Text, Text, callable, Text, Optional[Dict]) -> None

    code = inspect.getsource(command_func)
    code = dedent("".join(code.splitlines(True)[1:]))

    cmds.menuItem(
        menu_name,
        label=label,
        parent=parent,
        echoCommand=True,
        command=code,
        **args
    )
    
    
# ----

def open_synoptic():
    from mgear import synoptic
    synoptic.open()

    
# the top menu
cmds.menu(
    "HOGE_MENU_CONTAINER",
    label="hoge",
    parent='MayaWindow',
    tearOff=True,
    allowOptionBoxes=True
)
           
add_command_menu("animation_open_synoptic", "Synoptic", "HOGE_MENU_CONTAINER", open_synoptic)