code: def variant_key(variant, sort_alleles=True):
      """Gets a human-readable string key that is almost unique for Variant.
  
      Gets a string key that contains key information about the variant, formatted
      as:
  
        reference_name:start+1:reference_bases->alternative_bases
  
      where alternative bases is joined with a '/' for each entry in
      alternative_bases. The start+1 is so we display the position, which starts at
      1, and not the offset, which starts at 0.
  
      For example, a Variant(reference_name='20', start=10, reference_bases='AC',
      alternative_bases=['A', 'ACC']) would have a key of:
  
        20:11:AC->A/ACC
  
      The key is 'almost unique' in that the reference_name + start + alleles should
      generally occur once within a single VCF file, given the way the VCF
      specification works.
  
      Args:
        variant: nucleus.genomics.v1.Variant to make into a key.
        sort_alleles: bool. If True, the alternative_bases of variant will be sorted
          according to their lexicographic order. If False, the alternative_bases
          will be displayed in their order in the Variant.
  
      Returns:
        A str.
      """
      alts = variant.alternate_bases
      if sort_alleles:
          alts = sorted(alts)
      return "{}:{}:{}->{}".format(
          variant.reference_name,
          variant.start + 1,
          variant.reference_bases,
          "/".join(alts),
      )
  
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 40 for calling a global function with example usage: variant_key(variant, sort_alleles) and returns: str