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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 safe(self, parentheses=True):
 """ Returns a string representation with special characters replaced by safer characters for use in file names. """

        if not self:
            return ""
        string = str(self)
        string = string.replace("**", "_pow_")
        string = string.replace("*", "_mul_")
        string = string.replace("/", "_div_")
        string = string.replace("==", "_eq_")
        string = string.replace("<=", "_leq_")
        string = string.replace(">=", "_geq_")
        string = string.replace("<", "_lt_")
        string = string.replace(">", "_gt_")
        string = string.replace("&&", "_and_")
        string = string.replace("||", "_or_")
        string = string.replace("!", "not_")
        if parentheses:
            string = string.replace("(", "L")
            string = string.replace(")", "R")
        else:
            string = string.replace("(", "")
            string = string.replace(")", "")
        string = string.replace(" ", "")
        return string