code: def alt_bases_from_indices(alt_allele_indices, alternate_bases):
      """Get alt allele bases based on their indices.
  
      e.g. one alt allele: [0], ["C"] => "C"
      or with two alt alleles: [0,2], ["C", "TT", "A"] => "C-A"
  
      Args:
        alt_allele_indices: list of integers. Indices of the alt alleles for a
          particular example.
        alternate_bases: list of strings. All alternate alleles for the variant.
  
      Returns:
        str. Alt allele(s) at the indices, joined by '-' if more than 1.
      """
      alleles = [alternate_bases[i] for i in alt_allele_indices]
      # Avoiding '/' to support use in file paths.
      return "-".join(alleles)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import enum
  import math
  from typing import List, NamedTuple, Tuple
  from etils import epath
  from IPython import display
  import numpy
  from PIL import Image
  from PIL import ImageDraw
  from third_party.nucleus.protos import variants_pb2
label_desc: Use image node_id 16 for calling a global function with example usage: alt_bases_from_indices(alt_allele_indices, alternate_bases) and returns: str