PyCodeObject *
    PyCode_New(int argcount, int kwonlyargcount,
               int nlocals, int stacksize, int flags,
               PyObject *code, PyObject *consts, PyObject *names,
               PyObject *varnames, PyObject *freevars, PyObject *cellvars,
               PyObject *filename, PyObject *name, int firstlineno,
               PyObject *lnotab)
    {
        PyCodeObject *co;
        unsigned char *cell2arg = NULL;
        Py_ssize_t i, n_cellvars;

        /* Create mapping between cells and arguments if needed. */
        if (n_cellvars) {
            Py_ssize_t total_args = argcount + kwonlyargcount +
                ((flags & CO_VARARGS) != 0) + ((flags & CO_VARKEYWORDS) != 0); // *** 1 ***

            /* Find cells which are also arguments. */
            for (i = 0; i < n_cellvars; i++) {
                Py_ssize_t j;
                PyObject *cell = PyTuple_GET_ITEM(cellvars, i); 
                for (j = 0; j < total_args; j++) {
                    PyObject *arg = PyTuple_GET_ITEM(varnames, j);             // *** 2 ***
                    if (!PyUnicode_Compare(cell, arg)) {                       // *** 3 ***
                        cell2arg[i] = j;
                        used_cell2arg = 1;
                        break;
                    }   
                }   
            }
            
            // ...
        }