I have a dataframe with several columns showing percentage distributions.

I used `df["MaxColumn"] = df.idxmax(axis=1)` to identify the name of the column with the largest number for each row.

Now I need to do more calculations, i.e. add 1 to the cell with max value in each row.

I assumed that I could do something like `df[df["MaxColumn"]] += 1`, but I'm getting errors.

My dataframe:

```py
  Level1 Level2 Level3 MaxColumn
1    0.5    0.3    0.1    Level1
2    0.2    0.1    0.6    Level3

```

What I want is to add 1 to the max value in each row and get this:

```py
  Level1 Level2 Level3 MaxColumn
1    1.5    0.3    0.1    Level1
2    0.2    0.1    1.6    Level3

```