code: def get_format(variant_call, field_name, vcf_object=None):
      """Returns the value of the `field_name` FORMAT field.
  
      The `vcf_object` is used to determine the type of the resulting value. If it
      is a single value or a Flag, that single value will be returned. Otherwise,
      the list of values is returned.
  
      Args:
        variant_call: VariantCall proto. The VariantCall of interest.
        field_name: str. The name of the field to retrieve values from.
        vcf_object: (Optional) A VcfReader or VcfWriter object. If not None, the
          type of the field is inferred from the associated VcfReader or VcfWriter
          based on its name. Otherwise, the type is inferred if it is a reserved
          field.
      """
      if field_name == _GL:
          return get_gl(variant_call)
      if field_name == _GT:
          return get_gt(variant_call)
  
      if vcf_object is None:
          get_field_fn = vcf_constants.reserved_format_field_get_fn(
              field_name
          )
      else:
          get_field_fn = (
              vcf_object.field_access_cache.format_field_get_fn(
                  field_name
              )
          )
      return get_field_fn(variant_call.info, field_name)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from third_party.nucleus.protos import struct_pb2
  from third_party.nucleus.protos import variants_pb2
  from third_party.nucleus.util import struct_utils
  from third_party.nucleus.util import vcf_constants
label_desc: Use image node_id 2 for calling a global function with example usage: get_format(variant_call, field_name, vcf_object) and returns: get_field_fn, get_gl, get_gt