conditional formatting doesn't work after copying a sheet

Steps to Reproduce

1. load the attached file
B2 contains a conditional formatting rule that when B2 is not empty, its background color becomes red.
2. right click on the 1st sheet, select "copy"
3. select the newly copied sheet
4. type any string like abc at A2

Current Result

B2 background color doesn't change

Expected Result

B2 background color is red

Debug Information

io.keikai.model.impl.SheetImpl#copyToBook doesn't copy conditional formatting.