code: def test_ref_block_max_len_propagates_in_combiner():
      gvcfs = [
          "NA21123.hg38.g.vcf.gz",
          "NA21099.hg38.g.vcf.gz",
          "NA19747.hg38.g.vcf.gz",
      ]
      with hl.TemporaryDirectory() as tmpdir:
          vds_paths = []
          for i, gvcf in enumerate(gvcfs):
              p = os.path.join(tmpdir, f"{i}.vds")
              vds_paths.append(p)
              c = hl.vds.new_combiner(
                  output_path=p,
                  temp_path=tmpdir,
                  gvcf_paths=[
                      os.path.join(resource("gvcfs"), "1kg_chr22", gvcf)
                  ],
                  reference_genome="GRCh38",
                  import_interval_size=1000000000,
              )
              c.run()
  
          for path in vds_paths:
              vds = hl.vds.read_vds(path)
              assert (
                  hl.vds.VariantDataset.ref_block_max_length_field
                  in vds.reference_data.globals
              )
          final_path = os.path.join(tmpdir, "final.vds")
          hl.vds.new_combiner(
              output_path=final_path,
              temp_path=tmpdir,
              vds_paths=vds_paths,
              reference_genome="GRCh38",
          ).run()
          vds = hl.vds.read_vds(final_path)
          assert (
              hl.vds.VariantDataset.ref_block_max_length_field
              in vds.reference_data.globals
          )
  
file_path: hail/hail/python/test/hail/vds/test_combiner.py
imports: import os
  import pytest
  import hail
  from hail.utils.java import Env
  from hail.utils.misc import new_temp_file
  from hail.vds.combiner import combine_variant_datasets, new_combiner, load_combiner, transform_gvcf
  from hail.vds.combiner.combine import defined_entry_fields
  from ..helpers import resource, skip_when_service_backend, test_timeout, qobtest
label_desc: Use image node_id 7 for calling a global function with example usage: test_ref_block_max_len_propagates_in_combiner() without return types