code: def sg_argmax(tensor, opt):
      r
      opt += tf.sg_opt(axis=tensor.get_shape().ndims-1)
      return tf.argmax(tensor, opt.axis, opt.name)
docs: r"""Returns the indices of the maximum values along the specified axis.
      
      See `tf.argmax()` in tensorflow.
  
      Args:
        tensor: A `Tensor` (automatically given by chain).
        opt:
          axis: Target axis. Default is the last one.
          name: If provided, replace current tensor's name.
  
      Returns:
        A `Tensor`.