code: def pop(self):
          '''Return a new ImmutableVector with the last item removed.'''
          if self._length == 0:
              raise IndexError()
          newvec = ImmutableVector()
          newvec.tree = self.tree.remove(self._length-1)
          newvec._length = self._length-1
          return newvef pop(self):
          '''Return a new ImmutableVector with the last item removed.'''
          if self._length == 0:
              raise IndexError()
          newvec = ImmutableVector()
          newvec.tree = self.tree.remove(self._length-1)
          newvec._length = self._length-1
          return newvec
docs: Return a new ImmutableVector with the last item removed.