Funding for this research was provided by:
National Natural Science Foundation of China (81729003, 61871373)
Natural Science Foundation of Guangdong Province (2018A0303130132)
Text and Data Mining valid from 2019-07-26
Received: 28 February 2019
Accepted: 8 July 2019
First Online: 26 July 2019
: The authors declare that they have no competing interests.