HotRegion.set_num_cells reverts to default values for arguments not passed

[DevarshiChoudhury]

xpsi/xpsi/HotRegion.py

Line 247 in aaae64e

self.set_num_cells(sqrt_num_cells,

Based on the Hot Region Complexity notebook (input prompt 16 & 18), the expected behaviour of set_num_cells is to set specific cell resolution arguments manually and then run star.update, to update only the arguments passed and not others. Currently, the way the function is defined, it updates the arguments passed, but for other arguments that the function takes, it reverts to the default values instead of retaining the original user-defined values.

Solution would be to either update the doc to clarify this or improve the code to only update the argument passed. The latter is preferable so that the user doesn't have to restart the program just to update certain parameters.

P.S. set_num_rays and set_phases don't have any default arguments. It's yet to be investigated how they behave if only updating some of the arguments.