Return a BubbleTree instance.

        bbllines -- iterable of raw line, bubble-formatted
        oriented -- True: returned BubbleTree is oriented

def from_bubble_lines(bbllines:iter, oriented:bool=False,
                          symmetric_edges:bool=True) -> 'BubbleTree':
        """Return a BubbleTree instance.

        bbllines -- iterable of raw line, bubble-formatted
        oriented -- True: returned BubbleTree is oriented

        """
        return BubbleTree.from_bubble_data((utils.line_data(line)
                                            for line in bbllines),
                                           oriented=bool(oriented),
                                           symmetric_edges=symmetric_edges)