code: def get_loc(data, attr={'lr_mult':'0.01'}):
      
      loc = mx.symbol.Convolution(data=data, num_filter=30, kernel=(5, 5), stride=(2,2))
      loc = mx.symbol.Activation(data = loc, act_type='relu')
      loc = mx.symbol.Pooling(data=loc, kernel=(2, 2), stride=(2, 2), pool_type='max')
      loc = mx.symbol.Convolution(data=loc, num_filter=60, kernel=(3, 3), stride=(1,1), pad=(1, 1))
      loc = mx.symbol.Activation(data = loc, act_type='relu')
      loc = mx.symbol.Pooling(data=loc, global_pool=True, kernel=(2, 2), pool_type='avg')
      loc = mx.symbol.Flatten(data=loc)
      loc = mx.symbol.FullyConnected(data=loc, num_hidden=6, name="stn_loc", attr=attr)
      return loc
docs: the localisation network in lenet-stn, it will increase acc about more than 1%,
      when num-epoch >=15