How to display line numbers in IPython Notebook code cell by default

Question

I would like my default display for IPython notebook code cells to include line numbers.

I learned from Showing line numbers in IPython/Jupyter Notebooks that I can

Answer 1

Above didn't work for me in 2018

I found that inside ~/.jupyter/nbconfig/notebook.json I needed to add to add the following lines:

"CodeCell": {
  "cm_config": {
  "lineNumbers": true
}

inside the object that was there. So the final object would look like:

{
  "CodeCell": {
    "cm_config": {
      "lineNumbers": true
    }
  }
}