rqt_plot does not display topic

edit

When running my simulation on ros noetic, rqt_plot cannot display any topics anymore because of the following error:

Traceback (most recent call last):   File "/opt/ros/noetic/lib/python3/dist-packages/rqt_plot/plot_widget.py", line 230, in on_subscribe_topic_button_clicked
    self.add_topic(str(self.topic_edit.text())) File "/opt/ros/noetic/lib/python3/dist-packages/rqt_plot/plot_widget.py", line 290, in add_topic
    self._rosdata[topic_name] = ROSData(topic_name, self._start_time)  File "/opt/ros/noetic/lib/python3/dist-packages/rqt_plot/rosplot.py", line 108, in __init__
    self.field_evals = generate_field_evals(fields)   File "/opt/ros/noetic/lib/python3/dist-packages/rqt_plot/rosplot.py", line 207, in generate_field_evals
    raise RosPlotException("cannot parse field reference [%s]: %s" % (fields, str(e))) rqt_plot.rosplot.RosPlotException: cannot parse field reference [['external_torques[0]']]: module 'string' has no attribute 'atoi' Traceback (most recent call last):   File "/opt/ros/noetic/lib/python3/dist-packages/rqt_plot/rosplot.py", line 201, in generate_field_evals
    slot_num = string.atoi(rest[:rest.find(']')]) AttributeError: module 'string' has no attribute 'atoi'

So it is mostly about the last line concerning rosplot.py. I have found the cause of this problem on this forum: https://github.com/ros-visualization/rqt_plot/pull/57 Which seems to be a bug in rqt_plot.

And a solution on this forum: https://answers.ros.org/question/362951/rqt_plot-noetic-does-not-display-arrays-fields/ Which is to replace string.atoi with int(). However, I cannot edit the file rosplot.py since it is read only and also, I read everywhere that you shouldn't just edit files in ros rqt. How can I fix this bug then? Or is there a way to edit this file safely?

Solution: updating from rqt_plot 0.4.12 to 0.4.13.