code: def variant_is_deletion(variant, exclude_alleles=None):
      """Are all the variant's alt alleles deletions?
  
      Args:
        variant: nucleus.genomics.v1.Variant.
        exclude_alleles: list(str). The alleles in this list will be ignored.
  
      Returns:
        True if variant has at least one alt allele and all alts are deletions.
      """
      relevant_alts = _non_excluded_alts(
          variant.alternate_bases, exclude_alleles
      )
      if not relevant_alts:
          return False
      return all(
          is_deletion(variant.reference_bases, alt)
          for alt in relevant_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 15 for calling a global function with example usage: variant_is_deletion(variant, exclude_alleles) and returns: all, False