code: def _validate_signal(self, sig):
          
          if not isinstance(sig, int):
              raise TypeError('sig must be an int, not {!r}'.format(sig))
          if signal is None:
              raise RuntimeError('Signals are not supported')
          if not (1 <= sig < signal.NSIG):
              raise ValueError('sig {} out of range(1, {})'.format(sig, signal.NSIG))
          if sys.platform == 'win32':
              raise RuntimeError('Signals are not really supported on Windows')
docs: Internal helper to validate a signal.
  
          Raise ValueError if the signal number is invalid or uncatchable.
          Raise RuntimeError if there is a problem setting up the handler.