code: def buildEXPmask(self, chip, dqarr):
          
          log.info("Applying EXPTIME weighting to DQ mask for chip %s" %
                   chip)
          #exparr = self.getexptimeimg(chip)
          exparr = self._image[self.scienceExt,chip]._exptime
          expmask = exparr*dqarr
  
          return expmask.astype(np.float32)
docs: Builds a weight mask from an input DQ array and the exposure time
          per pixel for this chip.