code: def linear_act(x):
      return x
  
file_path: fastNLP/fastNLP/transformers/torch/activations.py
imports: import math
  from packaging import version
  from fastNLP.envs.imports import _NEED_IMPORT_TORCH
  from fastNLP.core.log import logger
label_desc: Use image node_id 7 for calling a global function with example usage: linear_act(x) and returns: x