code: def _protocol_to_cudf_column_string(
      col, allow_copy: bool
  ) -> Tuple[
      cudf.core.column.ColumnBase,
      Mapping[str, Optional[Tuple[_CuDFBuffer, ProtoDtype]]],
  ]:
      """
      Convert a string ColumnObject to cudf Column object.
      """
      # Retrieve the data buffers
      buffers = col.get_buffers()
  
      # Retrieve the data buffer containing the UTF-8 code units
      assert (
          buffers["data"] is not None
      ), "data buffer should never be None"
      data_buffer, data_dtype = buffers["data"]
      data_buffer = _ensure_gpu_buffer(
          data_buffer, data_dtype, allow_copy
      )
      encoded_string = build_column(
          data_buffer._buf,
          protocol_dtype_to_cupy_dtype(data_dtype),
      )
  
      # Retrieve the offsets buffer containing the index offsets demarcating
      # the beginning and end of each string
      assert (
          buffers["offsets"] is not None
      ), "not possible for string column"
      offset_buffer, offset_dtype = buffers["offsets"]
      offset_buffer = _ensure_gpu_buffer(
          offset_buffer, offset_dtype, allow_copy
      )
      offsets = build_column(
          offset_buffer._buf,
          protocol_dtype_to_cupy_dtype(offset_dtype),
      )
      offsets = offsets.astype("int32")
      cudfcol_str = build_column(
          None, dtype=cp.dtype("O"), children=(offsets, encoded_string)
      )
      return _set_missing_values(col, cudfcol_str, allow_copy), buffers
  
imports: import enum
  from collections import abc
  from typing import Any, Dict, Iterable, Mapping, Optional, Sequence, Tuple, cast
  import cupy
  import numpy
  from numba.cuda import as_cuda_array
  import rmm
  import cudf
  from cudf.core.buffer import Buffer, as_buffer
  from cudf.core.column import as_column, build_categorical_column, build_column
label_desc: Use image node_id 8 for calling a global function with example usage: _protocol_to_cudf_column_string(col, allow_copy) and returns: _set_missing_values,  buffers