docs: def bubble_to_gexf(bblfile:str, gexffile:str=None, oriented:bool=False):
      """Write in bblfile a graph equivalent to those depicted in bubble file"""
      tree = BubbleTree.from_bubble_file(bblfile, oriented=bool(oriented))
      gexf_converter.tree_to_file(tree, gexffile)
      return gexffile