def _enable_autopx(self):
        """Enable %autopx mode by saving the original run_cell and installing
        pxrun_cell.
        """
        # override run_cell
        self._original_run_cell = self.shell.run_cell
        self.shell.run_cell = self.pxrun_cell

        self._autopx = True
        print "%autopx enabled"
Enable %autopx mode by saving the original run_cell and installing
        pxrun_cell.