Is there an efficient way to add leading zeroes to a Dataframe's columns if:

1. The column contains integer values, and
2. For a given value of another column in the same Dataframe

E.g. for the following Dataframe, how do I create a new DataFrame that has leading zeroes in values in `col_2` if:

1. `col_2` are integer values (i.e. not `"text"` nor `"text2"`)
2. `col_1 == "A"`

Initial Dataframe:

```py
col_1   col_2
0   A   12345
1   B   863
2   A   text
3   C   893423
4   D   text2

```

Desired output Dataframe:

```py
col_1   col_2
0   A   00012345
1   B   863
2   A   text
3   C   893423
4   D   text2

```