makemask is called by cheese to create a cheese mask from the filtered source list. It can also be called standalone if the input files are deemed valid.
Warning and requirements: makemask was part of the esas package integrated into SAS, and was limited to work within the esas data reduction scheme. Generally, it is assumed that another former esas task, e.g., espfilt, has already been successfully run (in particular, for the input file's exposure to be used).
