code: def irafcrop(self, irafcropstring):
          
          irafcropstring = irafcropstring[1:-1] # removing the [ ]
          ranges = irafcropstring.split(",")
          xr = ranges[0].split(":")
          yr = ranges[1].split(":")
          xmin = int(xr[0])
          xmax = int(xr[1])+1
          ymin = int(yr[0])
          ymax = int(yr[1])+1
          self.crop(xmin, xmax, ymin, ymax)
docs: This is a wrapper around crop(), similar to iraf imcopy,
          using iraf conventions (100:199 will be 100 pixels, not 99).