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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 _prompt(self, prompt=None):
 """ Reads a line written by the user :param prompt: An optional prompt message :return: The read line, after a conversion to str """

        if prompt:
            # Print the prompt
            self.write(prompt)
            self.output.flush()

        # Read the line
        return to_str(self.input.readline())