Authors’ contributions
All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Xuemei Liang, Hongmei An, Huawei He, Baiyun Shen, and Zuoguo Ou. The first draft of the manuscript was written by Xuemei Liang, the final revision was prepared by Li Li, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.