text: """
  Context managers, i.e. things you can use with the 'with' statement.
  """
  
  
  import fcntl
  from contextlib import contextmanager
  from typing import Iterator, IO, Any, Union
  
  @contextmanager
  def flock(lockfile, shared=False):
      # type: (Union[int, IO[Any]], bool) -> Iterator[None]
      """Lock a file object using flock(2) for the duration of a 'with' statement.
  
         If shared is True, use a LOCK_SH lock, otherwise LOCK_EX."""
  
      fcntl.flock(lockfile, fcntl.LOCK_SH if shared else fcntl.LOCK_EX)
      try:
          yield
      finally:
          fcntl.flock(lockfile, fcntl.LOCK_UN)
  
  @contextmanager
  def lockfile(filename, shared=False):
      # type: (str, bool) -> Iterator[None]
      """Lock a file using flock(2) for the duration of a 'with' statement.
  
         If shared is True, use a LOCK_SH lock, otherwise LOCK_EX.
  
         The file is given by name and will be created if it does not exist."""
      with open(filename, 'w') as lock:
          with flock(lock, shared=shared):
              yield
  