human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "the helsinki neural machine translation system"
  Abstract: We introduce the Helsinki Neural Machine Translation system (HNMT) and how it is applied in the news translation task at WMT 2017, where it ranked first in both the human and automatic evaluations for English--Finnish. We discuss the success of English--Finnish translations and the overall advantage of NMT over a strong SMT baseline. We also discuss our submissions for English--Latvian, English--Chinese and Chinese--English.

Connected through hyperedge HE-1 (induced by source paper "the university of helsinki submissions to the wmt19 news translation task"):
  with members:
    - "selective attention for context aware neural machine translation"
    - "sentencepiece a simple and language independent subword tokenizer and detokenizer for neural text processing"
    - "cognate aware morphological segmentation for multilingual neural translation"
    - "the university of cambridge s machine translation systems for wmt18"
    - "neural machine translation with extended context"
    - "attention is all you need"
    - "opennmt open source toolkit for neural machine translation"
    - "improving neural machine translation models with monolingual data"

Connected through hyperedge HE-2 (induced by source paper "trivial transfer learning for low resource neural machine translation"):
  with members:
    - "training tips for the transformer model"
    - "phrase based neural unsupervised machine translation"
    - "bi directional neural machine translation with synthetic parallel data"
    - "the university of edinburgh s neural mt systems for wmt17"
    - "attention is all you need"
    - "unsupervised neural machine translation"
    - "transfer learning across low resource related languages for neural machine translation"
    - "six challenges for neural machine translation"

Connected through hyperedge HE-3 (induced by source paper "the memad submission to the wmt18 multimodal translation task"):
  with members:
    - "imagination improves multimodal translation"
    - "attention is all you need"
    - "opennmt open source toolkit for neural machine translation"
    - "mask r cnn"
    - "aggregated residual transformations for deep neural networks"
    - "pre translation for neural machine translation"
    - "google s multilingual neural machine translation system enabling zero shot translation"
    - "neural machine translation of rare words with subword units"

Connected through hyperedge HE-4 (induced by source paper "neural machine translation with extended context"):
  with members:
    - "achieving open vocabulary neural machine translation with hybrid word character models"
    - "google s neural machine translation system bridging the gap between human and machine translation"
    - "neural machine translation of rare words with subword units"
    - "neural machine translation by jointly learning to align and translate"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.CL(Computation and Language)