code: def get_frequency(frequency_str: str) -> Frequency:
      frequency_str = frequency_str.lower()
      if frequency_str not in frequency_str_to_enum:
          raise ReleaseTestConfigError(
              f"Frequency not found: {frequency_str}. Must be one of "
              f"{list(frequency_str_to_enum.keys())}."
          )
      return frequency_str_to_enum[frequency_str]
  
file_path: ray/release/ray_release/buildkite/settings.py
imports: import enum
  import os
  import subprocess
  from typing import Optional, Dict, Tuple
  from ray_release.exception import ReleaseTestConfigError
  from ray_release.logger import logger
  from ray_release.wheels import DEFAULT_BRANCH, get_buildkite_repo_branch
label_desc: Use image node_id 1 for calling a global function with example usage: get_frequency(frequency_str) and returns: frequency_str_to_enum