Iterates over texts in given HTML tree.

def _iter_texts(self, tree):
        """Iterates over texts in given HTML tree."""
        skip = (
            not isinstance(tree, lxml.html.HtmlElement)  # comments, etc.
            or tree.tag in self.skipped_tags
        )
        if not skip:
            if tree.text:
                yield Text(tree.text, tree, 'text')
            for child in tree:
                for text in self._iter_texts(child):
                    yield text
        if tree.tail:
            yield Text(tree.tail, tree, 'tail')