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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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