code: def init():
      """Initialize global variables from flag values."""
      global CHR20_FASTA
      global CHR20_BAM
      global CHR20_BAM_FIRST_HALF
      global CHR20_BAM_SECOND_HALF
      global NOCHR20_BAM
      global CHR20_CRAM
      global GOLDEN_TRAINING_EXAMPLES
      global GOLDEN_CALLING_CANDIDATES
      global GOLDEN_CANDIDATE_POSITIONS
      global GOLDEN_CALLING_EXAMPLES
      global CONFIDENT_REGIONS_BED
      global TRUTH_VARIANTS_VCF
      global TRUTH_VARIANTS_VCF_WITH_TYPES
      global GOLDEN_POSTPROCESS_INPUT
      global GOLDEN_POSTPROCESS_INPUT_SHARDED
      global GOLDEN_POSTPROCESS_OUTPUT
      global GOLDEN_POSTPROCESS_OUTPUT_PASS_ONLY
      global GOLDEN_POSTPROCESS_OUTPUT_COMPRESSED
      global GOLDEN_POSTPROCESS_GVCF_INPUT
      global GOLDEN_POSTPROCESS_GVCF_OUTPUT
      global GOLDEN_POSTPROCESS_GVCF_OUTPUT_COMPRESSED
      global GOLDEN_MAKE_EXAMPLES_RUN_INFO
      global WS_ALLELE_COUNT_LINEAR_MODEL
      global WS_ALLELE_COUNT_LINEAR_MODEL_PCKL
      global WS_VARIANT_READS_THRESHOLD_MODEL
      global GOLDEN_VCF_CANDIDATE_IMPORTER_POSTPROCESS_INPUT
      global GOLDEN_VCF_CANDIDATE_IMPORTER_POSTPROCESS_OUTPUT
  
      CHR20_FASTA = deepvariant_testdata(
          "input/ucsc.hg19.chr20.unittest.fasta.gz"
      )
      CHR20_BAM = deepvariant_testdata(
          "input/NA12878_S1.chr20.10_10p1mb.bam"
      )
      # # Here is how "NA12878_S1.chr20.10_10p1mb.first_half.bam"
      # # and "NA12878_S1.chr20.10_10p1mb.second_half.bam" are split
      # # from NA12878_S1.chr20.10_10p1mb.bam.
      # READS_FIRST_HALF=${TESTDATA_DIR}/NA12878_S1.chr20.10_10p1mb.first_half.bam
      # READS_SECOND_HALF=${TESTDATA_DIR}/NA12878_S1.chr20.10_10p1mb.second_half.bam
      # READS=${TESTDATA_DIR}/NA12878_S1.chr20.10_10p1mb.bam
      # samtools view -H ${READS} > /tmp/f1.sam
      # cp /tmp/f1.sam /tmp/f2.sam
      # # Because ${READS} has total of 52035 lines, we split in roughly half.
      # samtools view ${READS} | head -26000 >> /tmp/f1.sam
      # samtools view ${READS} | tail -26035 >> /tmp/f2.sam
      # samtools view -S -b /tmp/f1.sam > ${READS_FIRST_HALF}
      # samtools view -S -b /tmp/f2.sam > ${READS_SECOND_HALF}
      # samtools index ${READS_FIRST_HALF}
      # samtools index ${READS_SECOND_HALF}
      CHR20_BAM_FIRST_HALF = deepvariant_testdata(
          "input/NA12878_S1.chr20.10_10p1mb.first_half.bam"
      )
      CHR20_BAM_SECOND_HALF = deepvariant_testdata(
          "input/NA12878_S1.chr20.10_10p1mb.second_half.bam"
      )
      # # Here is how the "HG002_NIST_150bp_downsampled_30x.chr20.10_10p1mb.bam"
      # # file was created.
      # samtools view -hb HG002_NIST_150bp_downsampled_30x.bam \
      #     20:10,000,000-10,100,000 \
      #     > HG002_NIST_150bp_downsampled_30x.chr20.10_10p1mb.bam
      # samtools index HG002_NIST_150bp_downsampled_30x.chr20.10_10p1mb.bam
      NOCHR20_BAM = deepvariant_testdata(
          "input/HG002_NIST_150bp_downsampled_30x.chr20.10_10p1mb.bam"
      )
      CHR20_CRAM = deepvariant_testdata(
          "input/NA12878_S1.chr20.10_10p1mb.cram"
      )
      GOLDEN_TRAINING_EXAMPLES = deepvariant_testdata(
          "golden.training_examples.tfrecord.gz"
      )
      GOLDEN_CALLING_CANDIDATES = deepvariant_testdata(
          "golden.calling_examples.tfrecord.gz"
      )
      GOLDEN_CANDIDATE_POSITIONS = deepvariant_testdata(
          "golden.candidate_positions"
      )
      GOLDEN_CALLING_EXAMPLES = deepvariant_testdata(
          "golden.calling_examples.tfrecord.gz"
      )
      CONFIDENT_REGIONS_BED = deepvariant_testdata(
          "input/test_nist.b37_chr20_100kbp_at_10mb.bed"
      )
      TRUTH_VARIANTS_VCF = deepvariant_testdata(
          "input/test_nist.b37_chr20_100kbp_at_10mb.vcf.gz"
      )
      TRUTH_VARIANTS_VCF_WITH_TYPES = deepvariant_testdata(
          "input/with_types.test_nist.b37_chr20_4kbp_at_10mb.vcf.gz"
      )
      GOLDEN_POSTPROCESS_INPUT = deepvariant_testdata(
          "golden.postprocess_single_site_input.tfrecord.gz"
      )
      GOLDEN_POSTPROCESS_INPUT_SHARDED = deepvariant_testdata(
          "golden.postprocess_single_site_input-00000-of-00001.tfrecord.gz"
      )
      GOLDEN_POSTPROCESS_OUTPUT = deepvariant_testdata(
          "golden.postprocess_single_site_output.vcf"
      )
      GOLDEN_POSTPROCESS_OUTPUT_PASS_ONLY = deepvariant_testdata(
          "golden.postprocess_single_site_output.pass_only.vcf"
      )
      GOLDEN_POSTPROCESS_OUTPUT_COMPRESSED = deepvariant_testdata(
          "golden.postprocess_single_site_output.vcf.gz"
      )
      GOLDEN_POSTPROCESS_GVCF_INPUT = deepvariant_testdata(
          "golden.postprocess_gvcf_input.tfrecord.gz"
      )
      GOLDEN_POSTPROCESS_GVCF_OUTPUT = deepvariant_testdata(
          "golden.postprocess_gvcf_output.g.vcf"
      )
      GOLDEN_MAKE_EXAMPLES_RUN_INFO = deepvariant_testdata(
          "golden.training_examples.tfrecord.gz.run_info.pbtxt"
      )
      WS_ALLELE_COUNT_LINEAR_MODEL = deepvariant_testdata(
          "obsolete/window_selector_allele_count_linear.pbtxt"
      )
      WS_ALLELE_COUNT_LINEAR_MODEL_PCKL = deepvariant_testdata(
          "obsolete/window_selector_allele_count_linear.pckl"
      )
      WS_VARIANT_READS_THRESHOLD_MODEL = deepvariant_testdata(
          "obsolete/window_selector_variant_read_threshold.pbtxt"
      )
      GOLDEN_VCF_CANDIDATE_IMPORTER_POSTPROCESS_INPUT = deepvariant_testdata(
          "golden.vcf_candidate_importer_postprocess_single_site_input.tfrecord.gz"
      )
      GOLDEN_VCF_CANDIDATE_IMPORTER_POSTPROCESS_OUTPUT = deepvariant_testdata(
          "golden.vcf_candidate_importer_postprocess_single_site_output.vcf"
      )
  
      # For CustomizedClassesVariantLabeler:
      global CUSTOMIZED_CLASSES_GOLDEN_TRAINING_EXAMPLES
      CUSTOMIZED_CLASSES_GOLDEN_TRAINING_EXAMPLES = (
          deepvariant_testdata(
              "customized_classes.golden.training_examples.tfrecord.gz"
          )
      )
  
      # For VcfCandidateImporter:
      global GOLDEN_VCF_CANDIDATE_IMPORTER_TRAINING_EXAMPLES
      global GOLDEN_VCF_CANDIDATE_IMPORTER_CALLING_EXAMPLES
      global VCF_CANDIDATE_IMPORTER_VARIANTS
      GOLDEN_VCF_CANDIDATE_IMPORTER_TRAINING_EXAMPLES = deepvariant_testdata(
          "golden.vcf_candidate_importer.training_examples.tfrecord.gz"
      )
      GOLDEN_VCF_CANDIDATE_IMPORTER_CALLING_EXAMPLES = (
          deepvariant_testdata(
              "golden.vcf_candidate_importer_calling_examples.tfrecord"
          )
      )
      VCF_CANDIDATE_IMPORTER_VARIANTS = deepvariant_testdata(
          "input/vcf_candidate_importer.indels.chr20.vcf.gz"
      )
  
      # For alt-aligned pileups:
      global ALT_ALIGNED_ROWS_EXAMPLES
      global ALT_ALIGNED_DIFF_CHANNELS_EXAMPLES
      ALT_ALIGNED_ROWS_EXAMPLES = deepvariant_testdata(
          "golden.alt_aligned_pileup_rows_examples.tfrecord.gz"
      )
      ALT_ALIGNED_DIFF_CHANNELS_EXAMPLES = deepvariant_testdata(
          "golden.alt_aligned_pileup_diff_channels_examples.tfrecord.gz"
      )
  
      # For runtime-by-region in make_examples:
      global RUNTIME_BY_REGION
      global RUNTIME_BY_REGION_SHARDED
      RUNTIME_BY_REGION = deepvariant_testdata(
          "input/make_examples_runtime.tsv"
      )
      RUNTIME_BY_REGION_SHARDED = deepvariant_testdata(
          "input/make_examples_runtime@2.tsv"
      )
  
      # For allele_frequency with GRCh38:
      global VCF_WITH_ALLELE_FREQUENCIES
      global GRCH38_FASTA
      global AF_VCF_CHR20
      global AF_VCF_CHR21
      global AF_VCF_CHR20_21_WILDCARD
      global AF_VCF_CHR20_AND_21
      global GRCH38_CHR20_AND_21_BAM
      global GOLDEN_ALLELE_FREQUENCY_EXAMPLES
      VCF_WITH_ALLELE_FREQUENCIES = deepvariant_testdata(
          "input/allele_frequencies_vcf.vcf.gz"
      )
  
      # Fasta filtered to regions: chr20:1-10000000 and chr21:1-10000000.
      GRCH38_FASTA = deepvariant_testdata(
          "input/grch38.chr20_and_21_10M.fa.gz"
      )
      # VCFs filtered to chr20:1-100000 and chr21:5100000-5200000.
      AF_VCF_CHR20 = deepvariant_testdata(
          "input/cohort-chr20_100k.vcf.gz"
      )
      AF_VCF_CHR21 = deepvariant_testdata(
          "input/cohort-chr21_100k.vcf.gz"
      )
      AF_VCF_CHR20_AND_21 = deepvariant_testdata(
          "input/cohort-chr20_and_chr21_100k.vcf.gz"
      )
      AF_VCF_CHR20_21_WILDCARD = deepvariant_testdata(
          "input/cohort-chr2?_100k.vcf.gz"
      )
      # This bam filtered to regions: chr20:61001-62000 and chr21:5114000-5114999
      # and header is edited with the following to match the GRCH38_FASTA:
      # @SQ     SN:chr20        LN:10000000
      # @SQ     SN:chr21        LN:10000000
      GRCH38_CHR20_AND_21_BAM = deepvariant_testdata(
          "input/grch38_1k_subset_chr20_and_chr21.bam"
      )
      GOLDEN_ALLELE_FREQUENCY_EXAMPLES = deepvariant_testdata(
          "golden.allele_frequency_examples.tfrecord.gz"
      )
  
label_desc: Use image node_id 2 for calling a global function with example usage: init() without return types