Funding for this research was provided by:
National Natural Science Foundation of China (31701944)
Text and Data Mining valid from 2019-06-20
Received: 31 March 2019
Accepted: 14 June 2019
First Online: 20 June 2019
Ethics approval and consent to participate
: Not applicable.
: All the authors consent to publish.
: The authors declare that they have no competing interests.