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: "contracts in practice"
  Abstract: Contracts are a form of lightweight formal specification embedded in the program text. Being executable parts of the code, they encourage programmers to devote proper attention to specifications, and help maintain consistency between specification and implementation as the program evolves. The present study investigates how contracts are used in the practice of software development. Based on an extensive empirical analysis of 21 contract-equipped Eiffel, C#, and Java projects totaling more than 260 million lines of code over 7700 revisions, it explores, among other questions: 1 which kinds of contract elements preconditions, postconditions, class invariants are used more often; 2 how contracts evolve over time; 3 the relationship between implementation changes and contract changes; and 4 the role of inheritance in the process. It has found, among other results, that: the percentage of program elements that include contracts is above 33% for most projects and tends to be stable over time; there is no strong preference for a certain type of contract element; contracts are quite stable compared to implementations; and inheritance does not significantly affect qualitative trends of contract usage.

Connected through hyperedge HE-1 (induced by source paper "experience report on formally verifying parts of openjdk s api with key"):
  with members:
    - "lessons learned from microkernel verification specification is the new bottleneck"

Connected through hyperedge HE-2 (induced by source paper "learning likely invariants to explain why a program fails"):
  with members:
    - "inferring loop invariants by mutation dynamic analysis and static checking"
    - "casper debugging null dereferences with ghosts and causality traces"
    - "cause clue clauses error localization using maximum satisfiability"
    - "automated fault localization using potential invariants 1"

Connected through hyperedge HE-3 (induced by source paper "a comparative study of programming languages in rosetta code"):
  with members:
    - "design of an empirical study for comparing the usability of concurrent programming languages"
    - "benchmarking usability and performance of multicore languages"

Connected through hyperedge HE-4 (induced by source paper "automated fixing of programs with contracts"):
  with members:
    - "what good are strong specifications"
    - "code based automated program fixing"
    - "specifying reusable components"

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.SE(Software Engineering)