如何将3D尺寸不固定的3d数组展平为一维数组？

def flatten_3d_array(arr):
    result = []
    for element in arr:
        if isinstance(element, int):
            result.append(element)
        elif isinstance(element, list):
            result.extend(flatten_3d_array(element))
    return result

# 示例用法
arr_3d = [[[1, 2], [3, 4]], [[5, 6], [7, 8, 9]]]
flattened_arr = flatten_3d_array(arr_3d)
print(flattened_arr)

def flatten_3d_array(arr):
    result = []
    for i in range(len(arr)):
        for j in range(len(arr[i])):
            if isinstance(arr[i][j], int):
                result.append(arr[i][j])
            elif isinstance(arr[i][j], list):
                for k in range(len(arr[i][j])):
                    result.append(arr[i][j][k])
    return result

# 示例用法
arr_3d = [[[1, 2], [3, 4]], [[5, 6], [7, 8, 9]]]
flattened_arr = flatten_3d_array(arr_3d)
print(flattened_arr)