code: def format_filters(variant):
      """Returns a human-readable string showing the filters applied to variant.
  
      Returns a string with the filter field values of variant separated by commas.
      If the filter field isn't set, returns vcf_constants.MISSING_FIELD ('.').
  
      Args:
        variant: nucleus.genomics.v1.Variant.
  
      Returns:
        A string.
      """
      if variant.filter:
          return ",".join(variant.filter)
      else:
          return vcf_constants.MISSING_FIELD
  
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 6 for calling a global function with example usage: format_filters(variant) and returns: str, vcf_constants