docs: def intersection(self):
          """Compute the intersection with the given MOC.
  
          This command takes the name of a MOC file and forms the intersection
          of the running MOC with that file.
  
          ::
  
              pymoctool a.fits --intersection b.fits --output intersection.fits
          """
  
          if self.moc is None:
              raise CommandError('No MOC information present for intersection')
  
          filename = self.params.pop()
          self.moc = self.moc.intersection(MOC(filename=filename))