def record_line(self, frame, event, arg):  # pylint: disable=unused-argument
        """Records line execution time."""
        if event == 'line':
            if self.prev_timestamp:
                runtime = time.time() - self.prev_timestamp
                self.lines.append([self.prev_path, self.prev_lineno, runtime])
            self.prev_lineno = frame.f_lineno
            self.prev_path = frame.f_code.co_filename
            self.prev_timestamp = time.time()
        return self.record_line
Records line execution time.