code: def getexptimeimg(self,chip):
          
          sci_chip = self._image[self.scienceExt,chip]
          if sci_chip._wtscl_par == 'expsq':
              wtscl = sci_chip._exptime*sci_chip._exptime
          else:
              wtscl = sci_chip._exptime
  
          return np.ones(sci_chip.image_shape,dtype=sci_chip.image_dtype)*wtscl
docs: Notes
          =====
          Return an array representing the exposure time per pixel for the detector.
          This method will be overloaded for IR detectors which have their own
          EXP arrays, namely, WFC3/IR and NICMOS images.
  
          :units:
            None
  
          Returns
          =======
          exptimeimg : numpy array
              The method will return an array of the same shape as the image.