code: def check_staging_branch_is_available(
      config: Config, system: System
  ) -> ActionReturn:
      out = system.run(f"git branch --list {config.staging_branch}")
      if out:
          return FAILED(
              f"Release branch {config.staging_branch!r} ALREADY exists"
          )
      else:
          return PASSED(
              f"Release branch {config.staging_branch!r} does not already exist"
          )
  
imports: from __future__ import annotations
  import json
  import os
  from pathlib import Path
  from packaging.version import Version
  from .action import FAILED, PASSED, ActionReturn
  from .config import Config
  from .pipeline import StepType
  from .system import System
  from .util import skip_for_prerelease
label_desc: Use image node_id 10 for calling a global function with example usage: check_staging_branch_is_available(config, system) and returns: FAILED, PASSED