code: def num_output_channel(self):
      return self.last_channels
  
imports: import sys
  import os
  import mxnet
  import mxnet.ndarray
  import mxnet.gluon
  import mxnet.gluon.nn
  import mxnet.autograd
  import symbol_utils
  from config import config
label_desc: Use image node_id 3 for calling the MNasNet obj's underlying member method code with example usage: obj.num_output_channel() and returns: self