return a multidimensional vector from a function

i want to receive a vector that will have 3 two dimensional vectors
for example

Code:

int main()
{
vector<vector<vector<int>>>  ab=function()[0];
}
 
vector<vector<vector<int>>>  function()
{
vector<vector<vector<int>>>  return_vector;
vector<vector<int>> first;
vector<vector<int>> second;
vector<vector<int>> third;
 
 
//give values to three vectors and then isert them to return_vector
 
 
return_vector.push_back(first);
return_vector_push_back(second);
return_vector.push_back(third);
 
return return_vector;
}

i know that this is not the appropriate form but how can be that done??