text: Title: RandomIdentitySampler can have a repeating PID
  Body: This is a minor issue with the RandomIdentitySampler. The implementation does not necessarily guarantee that the N identities in the batch are unique. For example, ID 28 is sampled twice in this batch.
  
  ```
  tensor([ 554,  554,  554,  554,  195,  195,  195,  195,  399,  399,
           399,  399,  527,  527,  527,  527,   28,   28,   28,   28,
           501,  501,  501,  501,  252,  252,  252,  252,  136,  136,
           136,  136,  700,  700,  700,  700,  125,  125,  125,  125,
           120,  120,  120,  120,   68,   68,   68,   68,  577,  577,
           577,  577,  455,  455,  455,  455,   28,   28,   28,   28,
             9,    9,    9,    9,  387,  387,  387,  387,  564,  564,
           564,  564], device='cuda:0')
  ```
  Can be reproduced by calling any of the htri demo examples.