code: def build_sem_seg_head(cfg, input_shape):
      """
      Build a semantic segmentation head from `cfg.MODEL.SEM_SEG_HEAD.NAME`.
      """
      name = cfg.MODEL.SEM_SEG_HEAD.NAME
      return SEM_SEG_HEADS_REGISTRY.get(name)(cfg, input_shape)
  
imports: import numpy
  from typing import Callable, Dict, Optional, Tuple, Union
  import fvcore.nn.weight_init
  import torch
  from torch import nn
  from torch.nn import functional
  from detectron2.config import configurable
  from detectron2.layers import Conv2d, ShapeSpec, get_norm
  from detectron2.structures import ImageList
  from detectron2.utils.registry import Registry
  from ..backbone import Backbone, build_backbone
  from ..postprocessing import sem_seg_postprocess
  from .build import META_ARCH_REGISTRY
label_desc: Use image node_id 1 for calling a global function with example usage: build_sem_seg_head(cfg, input_shape) and returns: SEM_SEG_HEADS_REGISTRY