class_docstr: Simple wrapper for ClassyVision Vision Transformer model.
  This model is defined on the fly from a Vision Transformer base class and
  a configuration file.
code: def forward(
      self, x: torch.Tensor, out_feat_keys: List[str] = None
  ) -> List[torch.Tensor]:
      x = self.model(x)
      x = x.unsqueeze(0)
      return x
  
file_path: vissl/vissl/models/trunks/classy_vision_transformer.py
imports: import copy
  import logging
  from typing import List
  import torch
  import torch.nn
  from classy_vision.models import VisionTransformer
  from vissl.config import AttrDict
  from vissl.models.trunks import register_model_trunk
label_desc: Use image node_id 2 for calling the ClassyViT obj's underlying member method code with example usage: obj.forward(x, out_feat_keys) and returns: x