Kinetic parameters calculation

Hey there, i am new to openmc and i came across this novel feature in version 0.15.3 (installed using this procedure ( 2. Development Workflow — OpenMC Documentation )

I wanted to extract beta_eff and Lambda, however while running the model i get
what(): Invalid tally score “ifp-time-numerator”.”

Is this feature still under development?

Thank you in advance, best

Stefano

Ps. i’ll attach part of the code if it is helpful

_mc_model = openmc.Model(geometry, materials=materials, settings=settings , tallies=tallies)
_mc_model.add_kinetics_parameters_tallies(num_groups=6)
_mc_model.tallies.export_to_xml()
openmc.run()