1. School of Mathematics, Renmin University of China , Beijing 100872, China
2. Department of Mathematics, The University of Hong Kong , Pokfulam Road , Hong Kong
3. Key Laboratory of Systems Biology, Shanghai Institute of Biochemistry and Cell Biology, CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences , Shanghai 200031, China
4. Key Laboratory of Systems Health Science of Zhejiang Province, School of Life Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Chinese Academy of Sciences , Hangzhou 310024, China