Vector<vector<>> dictionary missing for TChain in PyROOT


I found out, that a part of PyROOT code I was using for TTrees does not work properly for TChain. Here is an example:

import ROOT
c = ROOT.TChain("teventefield")
v = ROOT.vector("vector<float>")()
c.SetBranchAddress("fft_mag_y", v)

Executing this I get an error message:

Error in <TChain::SetBranchAddress>: The class requested (vector<vector<float> >) for the branch "fft_mag_y" is an instance of an stl collection and does not have a compiled CollectionProxy. Please generate the dictionary for this collection (vector<vector<float> >) to avoid to write corrupted data.

However, it seems to work for TTrees:

import ROOT
f = ROOT.TFile("/data/GRAND/data_challenge1_pm_lwp/data/Coarse1.root")
t = f.Get("teventefield")
t.SetBranchAddress("fft_mag_y", v)

(no error, I can use the v normally)

Am I don’t something unexpected for TChain, or is there a part implemented in PyROOT for TTree but not for TChain?

I attach a tree that I’ve been using.
Coarse1.root (950.5 KB)

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ROOT Version: 6.26.11
Platform: Not Provided
Compiler: Not Provided

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