Replaces all placeholders with random numbers and letters.

        :param text: string to be parsed
        :returns: string with all numerical and letter placeholders filled in

def bothify(self, text='## ??', letters=string.ascii_letters):
        """
        Replaces all placeholders with random numbers and letters.

        :param text: string to be parsed
        :returns: string with all numerical and letter placeholders filled in
        """
        return self.lexify(self.numerify(text), letters=letters)