k2, k3 description in LMBTR descriptor

[fujiepku]

Dear developers,
I am a newcomer for dscribe package and I am trying to use LMBTR with dscribe-2.1 version to get descriptor for my system. However, I notice there are some changes regarding the k2, k3 implementations. When I try to use previous version of descriptor with "k2", "k3" at the same time. The error message came out saying "k2" is not defining. My question is how to use k2 and k3 feature at the same time with dscribe-2.1 version? Is there some new examples for this kind calculation?
Thanks a lot!

---

make_feature_LMBTR = LMBTR(
     species=species,
     k2 = {"geometry": {"function": "distance"},"grid": {"min": 0, "max": 5, "sigma" : 0.1, "n" : 200},"weighting": {"function": "exp", "scale": 0.5,
             "threshold": 1e-3}},
     k3 = {"geometry": {"function": "angle"},"grid": {"min": 0, "max": 180,
         "sigma" : 0.1, "n": 200},"weighting" : {"function": "exp", "scale": 0.5, "threshold": 1e-3}},
     periodic=True,
     sparse=False,
     normalization = "l2"
 )   

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