@Override public void clean(){
  m_storage=null;
  m_keys=null;
}

@ Override public void clean ( ) { m_storage = null ; m_keys = null ; }
frees the memory used by the kernel . ( useful with kernels which use cache . ) this function is called when the training is done . i . e . after that , eval will be called with id1 = = - 1 .
