def __getitem__(self, identifier):
        """
        For a given non-root node, access a child element by identifier.

        If the node is a root node, you may also access elements using
        either tuple format or the 'A.B.C' string format.
        """
        split_label = (tuple(identifier.split('.'))
                       if isinstance(identifier, str) else tuple(identifier))
        if len(split_label) == 1:
            identifier = split_label[0]
            if self.children in identifier:
                return self.__dict__[identifier]
            else:
                raise KeyError(identifier)
        path_item = self
        for identifier in split_label:
            path_item = path_item[identifier]
        return path_item
dataset/ETHPy150Open ioam/holoviews/holoviews/core/tree.py/AttrTree.__getitem__/swapped operands of `in`