code: def loss(self):
      assert (
          self.mode != "infer"
      ), "invalid loss calculationg in infer mode"
      cost = fluid.layers.sigmoid_cross_entropy_with_logits(
          x=self.logit, label=self.label_input
      )
      cost = fluid.layers.reduce_sum(cost, dim=-1)
      sum_cost = fluid.layers.reduce_sum(cost)
      self.loss_ = fluid.layers.scale(
          sum_cost, scale=self.num_gpus, bias_after_scale=False
      )
      return self.loss_
  
file_path: PaddleHub/modules/video/classification/videotag_tsn_lstm/resource/models/attention_lstm/attention_lstm.py
imports: import logging
  import paddle.fluid
  from paddle.fluid import ParamAttr
  from ..model import ModelBase
  from .lstm_attention import LSTMAttentionModel
label_desc: Use image node_id 6 for calling the AttentionLSTM obj's underlying member method code with example usage: obj.loss() and returns: self