code: def check_overscan(xstart, xsize, total_prescan_pixels=24,
                     total_science_pixels=4096):
      
      hasoverscan = False
      leading = 0
      trailing = 0
  
      if xstart < total_prescan_pixels:
          hasoverscan = True
          leading = abs(xstart - total_prescan_pixels)
  
      if (xstart + xsize) > total_science_pixels:
          hasoverscan = True
          trailing = abs(total_science_pixels -
                         (xstart + xsize - total_prescan_pixels))
  
      return hasoverscan, leading, trailing
docs: Check image for bias columns.
  
      Parameters
      ----------
      xstart : int
          Starting column of the readout in detector coordinates.
  
      xsize : int
          Number of columns in the readout.
  
      total_prescan_pixels : int
          Total prescan pixels for a single amplifier on a detector.
          Default is 24 for WFC.
  
      total_science_pixels : int
          Total science pixels across a detector.
          Default is 4096 for WFC (across two amplifiers).
  
      Returns
      -------
      hasoverscan : bool
          Indication if there are bias columns in the image.
  
      leading : int
          Number of bias columns on the A/C amplifiers
          side of the CCDs ("TRIMX1" in ``OSCNTAB``).
  
      trailing : int
          Number of bias columns on the B/D amplifiers
          side of the CCDs ("TRIMX2" in ``OSCNTAB``).