code: def fill_na(
      df: "SparkDataFrame",
      fill_val: Union[int, str, float],
      columns: List[str],
  ) -> "SparkDataFrame":
      return callZooFunc("float", "fillNa", df, fill_val, columns)
  
imports: from bigdl.dllib.utils.file_utils import callZooFunc
  from pyspark.sql.types import IntegerType, ShortType, LongType, FloatType, DecimalType, DoubleType, BooleanType
  from pyspark.sql.functions import broadcast, udf
  from bigdl.dllib.utils.log4Error import *
  import warnings
  from bigdl.dllib.utils.log4Error import *
  from typing import TYPE_CHECKING, Any, List, Optional, Tuple, Union
label_desc: Use image node_id 4 for calling a global function with example usage: fill_na(df, fill_val, columns) and returns: callZooFunc