def convert_graph_fmt(filename, fmt, output_dir=None):
automaton = Automaton(fromfile=filename)
filename_dir, filename_name = os.path.split(filename)
if output_dir:
filename_dir = output_dir
new_filename = os.path.join(filename_dir,
".".join([filename_name.split('.')[0], fmt]))
automaton.export(filename=new_filename)
