code: def frequency_converter(freq: str):
      parts = freq.split("_")
      if len(parts) == 1:
          return convert_base(parts[0])
      if len(parts) == 2:
          return convert_multiple(parts[0]) + convert_base(parts[1])
      raise ValueError(f"Invalid frequency string {freq}.")
  
imports: from datetime import datetime
  from distutils.util import strtobool
  from types import SimpleNamespace
  from typing import Dict
  import numpy
  from toolz import compose_left
  from gluonts import json
  from gluonts.exceptions import GluonTSDataError
label_desc: Use image node_id 2 for calling a global function with example usage: frequency_converter(freq) and returns: convert_base, unknown