def METHOD_NAME(self, tag):
    """ get tree node by tag
    :param tag: tag in dot notation (section.item)
    :return: dict or None if not found
    """
    node = self._template_in_data
    for item in tag.split('.'):
        if item in node:
            node = node[item]
        else:
            # not found
            return None
    # path found, return
    return node