code: def combine(ts):
      ts = Table(
          TableMapRows(
              ts._tir, combine_variant_rows(ts.row, ts.globals)._ir
          )
      )
      return ts.transmute_globals(
          __cols=hl.flatten(ts.g.map(lambda g: g.__cols))
      )
  
imports: import math
  from typing import Collection, Optional, Set, Union, List, Tuple, Dict
  import hail
  from hail import MatrixTable, Table
  from hail.experimental.function import Function
  from hail.expr import StructExpression, unify_all, construct_expr
  from hail.expr.expressions import expr_bool, expr_str
  from hail.genetics.reference_genome import reference_genome_type
  from hail.ir import Apply, TableMapRows
  from hail.typecheck import oneof, sequenceof, typecheck
  from ..variant_dataset import VariantDataset
label_desc: Use image node_id 20 for calling a global function with example usage: combine(ts) and returns: ts