Locating .dash-cell css classes

I am using the Overflow Strategies - Multiple Lines feature detailed in https://dash.plot.ly/datatable/sizing to wrap text in columns in an editable table. I am running into issues selecting a cell to edit with my mouse if the cell is originally blank (’’) or Null. You can, however, scroll into the cell and start typing that way. I suspect this has something to do with the .dash-cell and .dash-cell-value classes used in the code below, but I am having trouble finding them in the css files for dash-core-components. Do you know where I could find these classes?

```
dash_table.DataTable(
    style_data={'whiteSpace': 'normal'},
    css=[{
        'selector': '.dash-cell div.dash-cell-value',
        'rule': 'display: inline; white-space: inherit; overflow: inherit; text-overflow: inherit;'
    }],
    data=df_election.to_dict('rows'),
    columns=[{'id': c, 'name': c} for c in df_election.columns]
)
```