code: def open_external_file(self, fname):
          
          fname = encoding.to_unicode_from_fs(fname)
          if osp.isfile(fname):
              self.open_file(fname, external=True)
          elif osp.isfile(osp.join(CWD, fname)):
              self.open_file(osp.join(CWD, fname), external=True)
docs: Open external files that can be handled either by the Editor or the
          variable explorer inside Spyder.