docs: def format_signed(feature,  # type: Dict[str, Any]
                    formatter=None,  # type: Callable[..., str]
                    **kwargs
                    ):
      # type: (...) -> str
      """
      Format unhashed feature with sign.
  
      >>> format_signed({'name': 'foo', 'sign': 1})
      'foo'
      >>> format_signed({'name': 'foo', 'sign': -1})
      '(-)foo'
      >>> format_signed({'name': ' foo', 'sign': -1}, lambda x: '"{}"'.format(x))
      '(-)" foo"'
      """
      txt = '' if feature['sign'] > 0 else '(-)'
      name = feature['name']  # type: str
      if formatter is not None:
          name = formatter(name, **kwargs)
      return '{}{}'.format(txt, name)