title: tensorflow Optimizer.py "optimizer._get_variable_for" file function
body: <p>I am trying to implement an Optimizer in tensorflow, and have been looking at optimizer code from old version of tensorflow, and want to understand what does this function <code>_get_variable_for</code> do? It is the first function in the optimizer file.</p>
  
  <p>Any help would be appreciated.</p>
  
  <p>Thanking You.</p>