How to boost TLorentzVector with uproot

Dear experts,
I am currently trying to exploit TLorentz vectors in uproot, using the awkward and vector libs.
In particular, I am building these vectors:

import uproot
import awkward as ak
import vector
vector.register_awkward()   # any record named "Momentum4D" will be Lorentz

with<file>) as Y:

    vars = ["MC_t_pt", "MC_t_phi", "MC_t_eta", "MC_t_m", "MC_tbar_pt", "MC_tbar_phi", "MC_tbar_eta", "MC_tbar_m"]
    mttbar_arrays = Y.arrays(vars)

    t_vec ={
        "pt": mttbar_arrays.MC_t_pt,
        "phi": mttbar_arrays.MC_t_phi,
        "eta": mttbar_arrays.MC_t_eta,
        "mass": mttbar_arrays.MC_t_m,
    }, with_name="Momentum4D")

    tbar_vec ={
        "pt": mttbar_arrays.MC_tbar_pt,
        "phi": mttbar_arrays.MC_tbar_phi,
        "eta": mttbar_arrays.MC_tbar_eta,
        "mass": mttbar_arrays.MC_tbar_m,
    }, with_name="Momentum4D")

    top_boost = t_vec.BoostVector()
    tbar_boost = tbar_vec.BoostVector()

Then, as an error I get:

AttributeError: no field named 'BoostVector'

Is there a way to call the classic TLorentz vector functions in uproot 4?

uproot version: uproot 4
Platform: lxplus
Compiler: Not Provided

Hello @chiara_iannetta ,

I’m afraid uproot is not maintained by the ROOT team, this question is probably better suited for an uproot support forum.