text: """Helper function for interaction with the underlying operating system."""
  
  import glob
  import os
  import shutil
  from typing import Iterator, Optional
  
  
  def remove_file(file_path: str) -> None:
      """Remove file or directory including all its contents."""
      if os.path.isfile(file_path):
          os.remove(file_path)
      else:
          shutil.rmtree(file_path)
  
  
  def multi_glob(*patterns: str) -> Iterator[str]:
      """Perform glob search on all arguments."""
      for pattern in patterns:
          for file_path in glob.glob(pattern):
              yield file_path
  
  
  def get_env(variable: str) -> Optional[str]:
      """Get environment variable or None."""
      return os.environ.get(variable, None)
  