docs: 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)