code: def _compute_half_width(width):
      return int((width - 1) / 2)
  
imports: import itertools
  from typing import Iterable, List, Optional, Tuple
  from absl import logging
  import numpy
  from deepvariant import dv_constants
  from deepvariant import sample
  from deepvariant.protos import deepvariant_pb2
  from deepvariant.python import pileup_image_native
  from third_party.nucleus.io import fasta
  from third_party.nucleus.io import sam
  from third_party.nucleus.protos import reads_pb2
  from third_party.nucleus.protos import variants_pb2
  from third_party.nucleus.util import ranges
label_desc: Use image node_id 2 for calling a global function with example usage: _compute_half_width(width) and returns: int