title: Triplet loss tensorflow where anchor-positive pairs are defined upfront
body: <p>I am trying to implement triplet loss in Tensorflow where the triplets are obtained in an online mining way. In my particular problem, I already have the <code>anchor(image) - positive(text)</code> pairs. What I want to achieve is have the triplets <code>anchor(image) - positive(text) - negative(text)</code> and <code>anchor(text) - positive(image) - negative(image)</code> for <code>image-text</code> pairs in the batch.</p>
  
  <p>Let me know if you need any further information and looking forward to your answers!</p>