class_docstr: Custom Encoder with extended position embedding that is shift-invariant.
class_docstr_tok: ["Custom","Encoder","with","extended","position","embedding","that","is","shift-invariant","."]
code: def __init__(self, opt, *args, **kwargs):
      super().__init__(opt, *args, **kwargs)
      self.n_positions_init = opt.get("n_positions_init", None)
  
file_path: ParlAI/projects/msc/agents/long_tga.py
imports: import torch
  from typing import Optional, Tuple
  from parlai.agents.transformer.modules import TransformerDecoder, TransformerEncoder, TransformerGeneratorModel
  from parlai.agents.transformer.transformer import TransformerGeneratorAgent
  from parlai.core.opt import Opt
  from parlai.core.params import ParlaiParser
label_desc: Use image node_id 1 to create a new ShiftInvariantForwardEmbeddingMixin object  with example: obj = ShiftInvariantForwardEmbeddingMixin(opt)