I would like to convert string value HH:MM:SS.mmm to float value sec.milliseconds for arithmetic calculations. Is there a direct way to do this as currently I am doing it via split string function and it is a very tedious process. Dataframe looks like:

```
Col1
00:00:05.063
00:01:00.728
00:03:10.117

```

Output should look like

```
  5.063
 60.728
190.117

```

Appreciate any help.