为什么 Lua 在递归函数中创建了表内表？

我想把table中的每个值替换成另一个值。我的代码：

function substitute_in_table(requests)
    local function helper(r, result)
        for k, v in pairs(r) do
            if type(v) == "table" then
                result[k] = helper(v, result)
            else
                result[k] = 'someValue'
            end
        end
        return result
    end

    return helper(requests, {})
end

r = {
    request = {
        headers = "a",
        body = "b"
    }
}
result = substitute_in_table(r)
print(inspect(result))

结果是我得到了一个像这样的表：

{
   headers = "someValue"
   body = "someValue",
   request = {
      headers = "someValue"
      body = "someValue"
   }
}

但是期望的结果是

request = {
    headers = "someValue"
    body = "someValue"
}