def METHOD_NAME(self, node, results):
    """Returns the transformation for a given parse tree node.
    Args:
      node: the root of the parse tree that matched the fixer.
      results: a dict mapping symbolic names to part of the match.
    Returns:
      None, or a node that is a modified copy of the
      argument node.  The node argument may also be modified in-place to
      effect the same change.
    Subclass *must* override.
    """
    raise NotImplementedError()