[Bug]: Running error in the nnp example in notebook

[DRRXYY]

Email (Optional)

No response

Version

2023.9.9

Which OS(es) are you using?

• MacOS
• Windows
• Linux

What happened?

1、I encountered an error while running the nnp. train() code snippet。（RuntimeError: NNP Trainer has not been found.）

Code snippet

from maml.apps.pes import NNPotential

nnp = NNPotential()
nnp.train(
    train_structures=train_structures,
    train_energies=train_energies,
    train_forces=train_forces,
    cutoff_type=1,
    atom_energy={"Ni": -3.0, "Mo": -4.14},
    r_etas=[0.5, 2.0],
    a_etas=[0.5, 2.0],
    r_shift=[0.0],
    zetas=[1.0, 4.0],
    r_cut=4.2,
    hidden_layers=[4, 4],
    epochs=5,
)

Log output

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[zz11ss11zz]

@DRRXYY Hi, could you double check if the n2p2 package (https://compphysvienna.github.io/n2p2/) has been successfully installed in your system? And the nnp-train can be found by using which.