PVTU (multiple VTUs) to one VTU

I use the MPI program to run out the calculation results to generate pvtu (it is made up of many vtu), and I want to turn multiple vtu files into one vtu. If I want to use C++, which vtk API can I call to implement this function. I learned that the save data function of paraview can be exported to a VTU. I don’t know how it works.