Your task is to create a function called ```sum_arrays()``` in Python or ```addArrays``` in Javascript, which takes two arrays consisting of integers, and returns the sum of those two arrays.

The twist is that (for example) ```[3,2,9]``` does not equal ``` 3 + 2 + 9```, it would equal ```'3' + '2' + '9'``` converted to an integer for this kata, meaning it would equal ```329```. The output should be an array of the the sum  in a similar fashion to the input (for example, if the sum is ```341```, you would return ```[3,4,1]```). Examples are given below of what two arrays should return.
```python
[3,2,9],[1,2] --> [3,4,1]
[4,7,3],[1,2,3] --> [5,9,6]
[1],[5,7,6] --> [5,7,7]
```
If both arrays are empty, return an empty array.

In some cases, there will be an array containing a negative number as the first index in the array. In this case treat the whole number as a negative number. See below:
```python
[3,2,6,6],[-7,2,2,8] --> [-3,9,6,2] # 3266 + (-7228) = -3962
```

```python

USER_FILENAME = "<user_code>"
import sys, json, builtins
import math, heapq, bisect, itertools, functools, collections, statistics, fractions, decimal, operator, array, random, re, string, os, pathlib
try:
    import resource as _res
except Exception:
    _res = None
from collections import Counter, defaultdict, deque, OrderedDict
from functools import lru_cache, reduce
from itertools import accumulate, permutations, combinations, product
from math import gcd, ceil, floor, sqrt
from decimal import Decimal
try:
    from typing import *
except Exception:
    pass
try:
    sys.setrecursionlimit(1_000_000)
except Exception:
    pass
try:
    import site as _site
    try:
        _sys_sites = _site.getsitepackages() if hasattr(_site, "getsitepackages") else []
        for _p in _sys_sites:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
    try:
        _usp = _site.getusersitepackages()
        if isinstance(_usp, str):
            _usp = [_usp]
        for _p in _usp:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
except Exception:
    pass

def _disabled_input(*args, **kwargs):
    raise RuntimeError("input() is disabled in callable mode")
builtins.input = _disabled_input

ns = {"__name__": "__judge__"}  # prevent if __name__ == "__main__" blocks
for _k, _v in list(globals().items()):
    if not _k.startswith("_"):
        ns[_k] = _v
_CODE = 'def sum_arrays(arr1, arr2):\n    if not arr1 and not arr2: return []\n    if any([not arr1, not arr2]): return arr1 if not arr2 else arr2\n    a = str(int("".join([str(x) for x in arr1])) + int("".join([str(x) for x in arr2])))\n    if a == "0": return []\n    return [-int(a[1])] + [int(a[k]) for k in range(2, len(a))] if a[0] == "-" else [int(a[k]) for k in range(len(a))]'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'sum_arrays'
if _fn_name:
    if "Solution" in ns:
        try:
            _obj = ns["Solution"]()
            if hasattr(_obj, _fn_name):
                _target = getattr(_obj, _fn_name)
        except Exception:
            _target = None
    if _target is None and _fn_name in ns and callable(ns[_fn_name]):
        _target = ns[_fn_name]
# Fallback: if there's exactly one user-defined function, use it
if _target is None:
    _cands = [v for k, v in ns.items() if callable(v) and getattr(v, "__module__", "") in ("__judge__", "__main__")]
    _user_funcs = [c for c in _cands if getattr(c, "__name__", "").startswith("_") is False]
    if len(_user_funcs) == 1:
        _target = _user_funcs[0]
if _target is None:
    raise RuntimeError(f"Could not resolve callable '{_fn_name}'")

_raw = sys.stdin.read().strip()
if _raw:
    _parsed = json.loads(_raw)
    if isinstance(_parsed, dict):
        _kwargs = _parsed.get("kwargs", {})
        _args = _parsed.get("args", [])
    else:
        _args, _kwargs = _parsed, {}
else:
    _args, _kwargs = [], {}
if not isinstance(_args, (list, tuple)):
    _args = [_args]
_res = _target(*_args, **_kwargs)
try:
    sys.stdout.write(repr(_res) + "\n")
except Exception:
    pass

```

Measured memory_bytes: 6014