Add trivial MPS network with generate() and wire generate into NetworkProto

[Copilot]

• Add generate method to NetworkProto in model_dict.py with return type tuple[torch.Tensor, torch.Tensor, torch.Tensor, None]
• Add generate method (raises NotImplementedError) to all 3 WaveFunction classes in mlp.py
• Add generate method (raises NotImplementedError) to all 3 WaveFunction classes in transformers.py
• Create qmp/networks/mps.py with WaveFunction class:
  • Constructor params: sites, physical_dim, virtual_dim
  • forward(): compute MPS amplitude via tensor contraction with open boundary conditions
  • generate_unique(): raises NotImplementedError
  • generate(): autoregressive sampling returning (unique_configs, amplitudes, counts, None)
• Use NotImplementedError (not RuntimeError) in all generate stubs
• Align generate docstring style with generate_unique across model_dict.py and mps.py

Original prompt

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This section details on the original issue you should resolve

<issue_title>添加一个mps.py的网络</issue_title>
<issue_description>里面只含有一个平凡的网络, 输入参数是virtual dim和physical dim , 然后没有generate_unique这个函数(raise not implement error), 但是有一个generate函数. 同时给network proto加上generate函数, generate的输出应该是 tuple[torch.Tensor, torch.Tensor, torch.Tensor, None] 其中第三个参数是这个config被采样到的次数, 前面两个和generate unique一样. 目前已经存在的函数的def generate要raise not implemented error</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes 添加一个mps.py的网络 #194

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[hzhangxyz]

用 NotImplementedError. 另外, generate的注释中, 除非是新的那个返回值, 其他尽量保持和 generate_unique 字母级语言风格一致

[Copilot]

用 NotImplementedError. 另外, generate的注释中, 除非是新的那个返回值, 其他尽量保持和 generate_unique 字母级语言风格一致

Done in 03984c1. Changed all RuntimeError to NotImplementedError in the generate stubs (mlp.py, transformers.py) and generate_unique stub (mps.py), and aligned the generate docstrings in model_dict.py and mps.py to match the letter-level style of generate_unique.

[Copilot]

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