1322 def prettyformat(tree):

  1323     def _prettyformat(tree, level, lines):

  1324         if not isinstance(tree, tuple) or tree[0] in ('string', 'symbol'):

  1325             lines.append((level, str(tree)))

  1326         else:

  1327             lines.append((level, '(%s' % tree[0]))

  1328             for s in tree[1:]:

  1329                 _prettyformat(s, level + 1, lines)

  1330             lines[-1:] = [(lines[-1][0], lines[-1][1] + ')')]

  1331 

  1332     lines = []

  1333     _prettyformat(tree, 0, lines)

  1334     output = '\n'.join(('  '*l + s) for l, s in lines)

  1335     return output

  1336