code: def build(self):
      self._build_word_embedding()
      self._init_text_embeddings("text")
      self._init_feature_encoders("image")
      self._init_feature_projectors("image")
      self._init_feature_embeddings("image")
      self._init_combine_layer("image", "text")
      self._init_classifier(self._get_classifier_input_dim())
      self._init_extras()
  
imports: import copy
  import omegaconf
  import torch
  from mmf.common.registry import registry
  from mmf.models.base_model import BaseModel
  from mmf.modules.embeddings import ImageFeatureEmbedding, MultiHeadImageFeatureEmbedding, PreExtractedEmbedding, TextEmbedding
  from mmf.modules.layers import ClassifierLayer, ModalCombineLayer
  from mmf.utils.build import build_image_encoder
  from torch import nn
label_desc: Use image node_id 3 for calling the PythiaMultiHead obj's underlying member method code with example usage: obj.build() without return types