Funding for this research was provided by:
the Training Program of the National Natural Science Foundation of China (5101049170806)
Text and Data Mining valid from 2019-10-11
Received: 6 June 2019
Accepted: 1 October 2019
First Online: 11 October 2019
Ethics approval and consent to participate
: Not applicable as this article does not contain any studies with human participants or animals by any of the authors.
: Not applicable.
: The authors declare that they have no competing interests.