code: def is_insertion(ref, alt):
      """Is alt an insertion w.r.t. ref?
  
      Args:
        ref: A string of the reference allele.
        alt: A string of the alternative allele.
  
      Returns:
        True if alt is an insertion w.r.t. ref.
      """
      return len(ref) < len(alt)
  
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 19 for calling a global function with example usage: is_insertion(ref, alt) and returns: unknown