def get_text_range(self, node):
    """
    After mark_tokens() has been called, returns the (startpos, endpos) positions in source text
    corresponding to the given node. Returns (0, 0) for nodes (like `Load`) that don't correspond
    to any particular text.
    """
    if not hasattr(node, 'first_token'):
      return (0, 0)

    start = node.first_token.startpos
    if any(match_token(t, token.NEWLINE) for t in self.get_tokens(node)):
      # Multi-line nodes would be invalid unless we keep the indentation of the first node.
      start = self._text.rfind('\n', 0, start) + 1

    return (start, node.last_token.endpos)
After mark_tokens() has been called, returns the (startpos, endpos) positions in source text
    corresponding to the given node. Returns (0, 0) for nodes (like `Load`) that don't correspond
    to any particular text.