I have a dataframe in which I would like to duplicate rows but with the values swapped. Original is shown as `df1` and desired is `df2`:

```
df1

GameID     Team1ID     Team2ID     Team1Abb      Team2Abb    Team1PTS    Team2PTS
   0        1001        1023         TOR           ATL          99          86
   1        1004        1003         DAL           POR          102         100

df2

GameID     Team1ID     Team2ID     Team1Abb      Team2Abb    Team1PTS    Team2PTS
   0        1001        1023         TOR           ATL          99          86
   0        1023        1001         ATL           TOR          86          99
   1        1004        1003         DAL           POR          102         100
   1        1003        1004         POR           DAL          100         102

```