code: def test_summarize_variants(self):
      mt = hl.utils.range_matrix_table(3, 3)
      variants = hl.literal(
          {
              0: hl.Struct(
                  locus=hl.Locus("1", 1), alleles=["A", "T", "C"]
              ),
              1: hl.Struct(
                  locus=hl.Locus("2", 1), alleles=["A", "AT", "@"]
              ),
              2: hl.Struct(
                  locus=hl.Locus("2", 1), alleles=["AC", "GT"]
              ),
          }
      )
      mt = mt.annotate_rows(**variants[mt.row_idx]).key_rows_by(
          "locus", "alleles"
      )
      r = hl.summarize_variants(mt, show=False)
      self.assertEqual(r.n_variants, 3)
      self.assertEqual(r.contigs, {"1": 1, "2": 2})
      self.assertEqual(
          r.allele_types,
          {"SNP": 2, "MNP": 1, "Unknown": 1, "Insertion": 1},
      )
      self.assertEqual(r.allele_counts, {2: 1, 3: 2})
  
imports: import unittest
  import hail
  from ..helpers import *
label_desc: Use image node_id 14 for calling the Tests obj's underlying member method code with example usage: obj.test_summarize_variants() without return types