def _SetCompleted(self):
    """Atomically marks the breakpoint as completed.

    Returns:
      True if the breakpoint wasn't marked already completed or False if the
      breakpoint was already completed.
    """
    with self._lock:
      if self._completed:
        return False
      self._completed = True
      return True
Atomically marks the breakpoint as completed.

    Returns:
      True if the breakpoint wasn't marked already completed or False if the
      breakpoint was already completed.