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: "tree automata and tree grammars"
  Abstract: Lecture notes on tree language theory, in particular recognizable tree languages and finite state tree transformations.

Connected through hyperedge HE-1 (induced by source paper "linear bounded composition of tree walking tree transducers linear size increase and complexity"):
  with members:
    - "xml navigation and transformation by tree walking automata and transducers with visible and invisible pebbles"
    - "context free grammars with storage"
    - "the complexity of translation membership for macro tree transducers"

Connected through hyperedge HE-2 (induced by source paper "multiple context free tree grammars lexicalization and characterization"):
  with members:
    - "streaming tree transducers"
    - "deciding unambiguity and sequentiality from a finitely ambiguous max plus automaton"
    - "mso definable string transductions and two way finite state transducers"

Connected through hyperedge HE-3 (induced by source paper "weighted regular tree grammars with storage"):
  with members:
    - "context free grammars with storage"

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.FL(Formal Languages and Automata Theory)