code: def ingest_dark(self):
          
  
          self.dark = extract_dark(self.hdulist[0].header, self.hdulist[1])
  
          # If BIAS or DARK, set dark to zeros
          if self.dark is None:
              self.dark = np.zeros_like(self.science)
              return
  
          # Apply the dark subtraction if necessary.
          # Effect of DARK on ERR is insignificant for de-striping.
          if self.darkcorr != 'COMPLETE':
              self.science = self.science - self.dark
docs: Process dark.