title: How to change the default optimizer in detectron2
body: <p>So from what I can tell by reading the <a href="https://detectron2.readthedocs.io/en/latest/modules/solver.html" rel="nofollow noreferrer">docs</a>, the default optimizer used in detectron2 is SGD with momentum. But I was wondering if there is a way to change the default optimizer to something like Adam for example.</p>
  <p>The closest I was able to get to was by looking at <code>cfg.SOLVER</code> attributes; specifically <code>cfg.SOLVER.OPTIMIZER</code>. I even took a look at their <a href="https://github.com/facebookresearch/detectron2/blob/2249be38968f896772eb5b5d3b8a248b9fc7e937/detectron2/solver/build.py#L133" rel="nofollow noreferrer">source code</a> to see if different optimizer options were available.</p>
  <p>However, I was unable to change the optimizer type.</p>
  <p>Any help will be greatly appreciated!</p>