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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 get_exp_dir_num(parent_dir: str) -> int: """ Gets the number of the current experiment directory."""

    return max([int(fn.split(".")[0])
                for fn in os.listdir(parent_dir) if fn.split(".")[0].isdigit()]
                    + [-1])