Quoting: https://github.com/apache/incubator-mxnet/blob/master/scala-package/core/src/main/scala/ml/dmlc/mxnet/NDArray.scala#L545-L546
* WARNING: it is your responsibility to clear this object through dispose(). * NEVER rely on the GC strategy Is there a way to say "dispose all ndarrays of this context" ?
