Funding for this research was provided by:
National Natural Science Foundation of China (21473153, 21872119)
Text and Data Mining valid from 2019-03-05
Received: 18 October 2018
Accepted: 25 February 2019
First Online: 5 March 2019
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.