code: def head(model_name: str, **kwargs):
      model_list = ["linear", "acar"]
      if model_name == "linear":
          model = LinearHead(**kwargs)
      elif model_name == "acar":
          model = ACARHead(**kwargs)
      else:
          raise ValueError(
              f"Expected element in {model_list} but got: {model_name}."
          )
      return model
  
file_path: towhee/towhee/models/acar_net/head.py
imports: import math
  import torch
  from torch import nn
  import torchvision
label_desc: Use image node_id 1 for calling a global function with example usage: head(model_name) and returns: model