Funding for this research was provided by:
National Natural Science Foundation of China (81672787)
Text and Data Mining valid from 2019-10-08
Received: 1 June 2019
Accepted: 3 September 2019
First Online: 8 October 2019
Ethics approval and consent to participate
: Not applicable.
: All authors have read and consent to the publication of this research article.
: The authors declare that they have no competing interests.