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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 poll_error(self):
 """ Append lines from stderr to self.errors. Returns: list: The lines added since last call """

        if self.block:
            return self.error

        new_list = self.error[self.old_error_size:]
        self.old_error_size += len(new_list)
        return new_list