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: "structural complexity of multi valued partial functions computed by nondeterministic pushdown automata"
  Abstract: This paper continues a systematic and comprehensive study on the structural properties of CFL functions, which are in general multi-valued partial functions computed by one-way one-head nondeterministic pushdown automata equipped with write-only output tapes (or pushdown transducers), where CFL refers to a relevance to context-free languages. The CFL functions tend to behave quite differently from their corresponding context-free languages. We extensively discuss containments, separations, and refinements among various classes of functions obtained from the CFL functions by applying Boolean operations, functional composition, many-one relativization, and Turing relativization. In particular, Turing relativization helps construct a hierarchy over the class of CFL functions. We also analyze the computational complexity of optimization functions, which are to find optimal values of CFL functions, and discuss their relationships to the associated languages.

Connected through hyperedge HE-1 (induced by source paper "not all multi valued partial cfl functions are refined by single valued functions"):
  with members:
    - "oracle pushdown automata nondeterministic reducibilities and the cfl hierarchy over the family of context free languages"
    - "immunity and pseudorandomness of context free languages"
    - "pseudorandom generators against advised context free languages"
    - "swapping lemmas for regular and context free languages"
    - "theory of one tape linear time turing machines"

Connected through hyperedge HE-2 (induced by source paper "uniform circuit and logarithmic space approximations of refined combinatorial optimization problems"):
  with members:
    - "optimization randomized approximability and boolean constraint satisfaction problems"

Connected through hyperedge HE-3 (induced by source paper "pseudorandom generators against advised context free languages"):
  with members:
    - "oracle pushdown automata nondeterministic reducibilities and the cfl hierarchy over the family of context free languages"
    - "immunity and pseudorandomness of context free languages"
    - "the roles of advice to one tape linear time turing machines and finite automata"
    - "swapping lemmas for regular and context free languages"
    - "theory of one tape linear time turing machines"

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)