code: def gen_cols_name(columns, name_sep="_"):
      if isinstance(columns, str):
          return columns
      elif isinstance(columns, list):
          return name_sep.join(columns)
      else:
          raise ValueError("item should be either str or list of str")
  
imports: from zoo.common.utils import callZooFunc
  from pyspark.sql.types import IntegerType, ShortType, LongType, FloatType, DecimalType, DoubleType
label_desc: Use image node_id 22 for calling a global function with example usage: gen_cols_name(columns, name_sep) and returns: columns, name_sep