def _as_string_type(index_ops: IndexOpsLike, dtype: Union[(str, type, Dtype)], *, null_str: str=str(None)) -> IndexOpsLike:
    'Cast `index_ops` to StringType Spark type, given `dtype` and `null_str`,\n    representing null Spark column. Note that `null_str` is for non-extension dtypes only.\n    '
    spark_type = StringType()
    if isinstance(dtype, extension_dtypes):
        scol = index_ops.spark.column.cast(spark_type)
    else:
        casted = index_ops.spark.column.cast(spark_type)
        scol = F.when(index_ops.spark.column.isNull(), null_str).otherwise(casted)
    return index_ops._with_new_scol(scol, field=index_ops._internal.data_fields[0].copy(dtype=dtype, spark_type=spark_type))
Cast `index_ops` to StringType Spark type, given `dtype` and `null_str`,
representing null Spark column. Note that `null_str` is for non-extension dtypes only.
def _as_string_type(index_ops: IndexOpsLike, dtype: Union[(str, type, Dtype)], *, null_str: str=str(None)) -> IndexOpsLike:
    'Cast `index_ops` to StringType Spark type, given `dtype` and `null_str`,\n    representing null Spark column. Note that `null_str` is for non-extension dtypes only.\n    '
    spark_type = StringType()
    if isinstance(dtype, extension_dtypes):
        scol = index_ops.spark.column.cast(spark_type)
    else:
        casted = index_ops.spark.column.cast(spark_type)
        scol = F.when(index_ops.spark.column.isNull(), null_str).otherwise(casted)
    return index_ops._with_new_scol(scol, field=index_ops._internal.data_fields[0].copy(dtype=dtype, spark_type=spark_type))