code: def calc_ac(variant):
      """Returns a list of alt counts based on variant.calls."""
      counts = [0] * len(variant.alternate_bases)
      for call in variant.calls:
          for gt in call.genotype:
              if gt > 0:
                  counts[gt - 1] += 1
      return counts
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import collections
  import enum
  import itertools
  import six
  from third_party.nucleus.protos import variants_pb2
  from third_party.nucleus.util import ranges
  from third_party.nucleus.util import variantcall_utils
  from third_party.nucleus.util import vcf_constants
label_desc: Use image node_id 45 for calling a global function with example usage: calc_ac(variant) and returns: counts