[trainers] Fixed the SiameseTrainer validation

6 jobs for tf-slim in 11 minutes and 48 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #78896
conda-linux
build_linux_27

00:02:34

passed #78897
conda-linux
build_linux_35

00:03:04

passed #78898
conda-linux
build_linux_36

00:03:08

 
  Test
passed #78899
conda-linux
test_linux_27

00:08:12

passed #78900
conda-linux
test_linux_35

00:08:17

passed #78901
conda-linux
test_linux_36

00:08:35