code: def localize(
      data: DatetimeColumn, zone_name: str, ambiguous, nonexistent
  ) -> DatetimeTZColumn:
      if ambiguous != "NaT":
          raise NotImplementedError(
              "Only ambiguous='NaT' is currently supported"
          )
      if nonexistent != "NaT":
          raise NotImplementedError(
              "Only nonexistent='NaT' is currently supported"
          )
      if isinstance(data, DatetimeTZColumn):
          raise ValueError(
              "Already localized. "
              "Use `tz_convert` to convert between time zones."
          )
      dtype = pd.DatetimeTZDtype(data._time_unit, zone_name)
      ambiguous, nonexistent = _find_ambiguous_and_nonexistent(
          data, zone_name
      )
      localized = cast(
          DatetimeColumn,
          data._scatter_by_column(
              data.isnull() | (ambiguous | nonexistent),
              cudf.Scalar(cudf.NaT, dtype=data.dtype),
          ),
      )
      gmt_data = local_to_utc(localized, zone_name)
      return cast(
          DatetimeTZColumn,
          build_column(
              data=gmt_data.base_data,
              dtype=dtype,
              mask=localized.base_mask,
              size=gmt_data.size,
              offset=gmt_data.offset,
          ),
      )
  
imports: import os
  import zoneinfo
  from functools import lru_cache
  from typing import Tuple, cast
  import numpy
  import pandas
  import cudf
  from cudf._lib.labeling import label_bins
  from cudf._lib.search import search_sorted
  from cudf._lib.timezone import make_timezone_transition_table
  from cudf.core.column.column import as_column, build_column
  from cudf.core.column.datetime import DatetimeColumn, DatetimeTZColumn
  from cudf.core.dataframe import DataFrame
  from cudf.utils.dtypes import _get_base_dtype
label_desc: Use image node_id 6 for calling a global function with example usage: localize(data, zone_name, ambiguous, nonexistent) and returns: cast