Funding for this research was provided by:
National Natural Science Foundation of China (31570331)
Text and Data Mining valid from 2019-10-28
Received: 20 August 2019
Accepted: 14 October 2019
First Online: 28 October 2019
Ethics approval and consent to participate
: Not applicable.
: The manuscript is approved by all authors for publication.
: The authors declare that they have no competing interests.