Ethics approval and consent to participate
The ethical approval or individual consent was not applicable.
Availability of data and materials
All data and materials used in this work were publicly available.
Consent for publication
Not applicable.
Funding
DH was supported by General Research Fund (15205119) of Research Grants Council of Hong Kong and an Alibaba-Hong Kong Polytechnic University Collaborative Research project.
Disclaimer
The funding agencies had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; or decision to submit the manuscript for publication.
Acknowledgements
None.
Consent for publicationCompeting Interests
DH was supported by an Alibaba-Hong Kong Polytechnic University Collaborative Research project. Other authors declare no competing interests.
Authors' Contributions
All authors conceived the study, carried out the analysis, discussed the results, drafted the first manuscript, critically read and revised the manuscript, and gave final approval for publication.