code: def populate_buffer(self):
      state = ParserState(self.parser)
      for _ in range(2):
          state.buffer_stackrnn.push(
              torch.zeros(1, 30), Element("Token")
          )
      return state
  
imports: import unittest
  from collections import Counter
  import torch
  import torch.nn
  from pytext.common.constants import Stage
  from pytext.config.module_config import PoolingType
  from pytext.legacy.vocab import Vocab
  from pytext.models.embeddings import DictEmbedding, EmbeddingList, WordEmbedding
  from pytext.models.semantic_parsers.rnng.rnng_data_structures import CompositionalNN, CompositionalSummationNN, Element, ParserState, StackLSTM
  from pytext.models.semantic_parsers.rnng.rnng_parser import RNNGParser
label_desc: Use image node_id 2 for calling the RNNGParserTest obj's underlying member method code with example usage: obj.populate_buffer() and returns: state