code: def pad(df, cols, seq_len, mask_cols):
      df = (
          callZooFunc("float", "mask", df, mask_cols, seq_len)
          if mask_cols
          else df
      )
      df = callZooFunc("float", "postPad", df, cols, seq_len)
      return df
  
imports: from zoo.common.utils import callZooFunc
  from pyspark.sql.types import IntegerType, ShortType, LongType, FloatType, DecimalType, DoubleType
label_desc: Use image node_id 16 for calling a global function with example usage: pad(df, cols, seq_len, mask_cols) and returns: df