You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: lib.rs
    path of file: ./repos/pyo3/examples/string-sum/src
    
    the code of the file until where you have to start completion: use std::os::raw::{c_char, c_long};
use std::ptr;

use pyo3_ffi::*;

static mut MODULE_DEF: PyModuleDef = PyModuleDef {
    m_base: PyModuleDef_HEAD_INIT,
    m_name: "string_sum\0".as_ptr().cast::<c_char>(),
    m_doc: "A Python module written in Rust.\0"
        .as_ptr()
        .cast::<c_char>(),
    m_size: 0,
    m_methods: unsafe { METHODS as *const [PyMethodDef] as *mut PyMethodDef },
    m_slots: std::ptr::null_mut(),
    m_traverse: None,
    m_clear: None,
    m_free: None,
};

static mut METHODS: &[PyMethodDef] = &[
    PyMethodDef {
        ml_name: "sum_as_string\0".as_ptr().cast::<c_char>(),
        ml_meth: PyMethodDefPointer {
            _PyCFunctionFast: sum_as_string,
        },
        ml_flags: METH_FASTCALL,
 
    
unsafe fn parse_arg_as_i32(obj: *mut PyObject, n_arg: usize) -> Option<i32> {
    if PyLong_Check(obj) == 0 {
        let msg = format!(
            "sum_as_string expected an int for positional argument {}\0",
            n_arg
        );
        PyErr_SetString(PyExc_TypeError, msg.as_ptr().cast::<c_char>());
        return None;
    }

    // Let's keep the behaviour consistent on platforms where `c_long` is bigger than 32 bits.
    // In particular, it is an i32 on Windows but i64 on most Linux systems
    let mut overflow = 0;
    let i_long: c_long = PyLong_AsLongAndOverflow(obj, &mut overflow);

    if overflow != 0 {
        raise_overflowerror(obj);
        None
    } else if let Ok(i) = i_long.try_into() {
        Some(i)
    } else {
        raise_overflowerror(obj);
        None
    }
}