code: def _check_negatives(numbers):
      "Raise warning for negative numbers."
  
      negatives = filter(lambda x: x < 0, filter(None, numbers))
      if any(negatives):
          neg_values = ', '.join(map(str, negatives))
          msg = 'Found negative value(s): {0!s}. '.format(neg_values)
          msg += 'While not forbidden, the output will look unexpected.'
          warnings.warn(msgf _check_negatives(numbers):
      "Raise warning for negative numbers."
  
      negatives = filter(lambda x: x < 0, filter(None, numbers))
      if any(negatives):
          neg_values = ', '.join(map(str, negatives))
          msg = 'Found negative value(s): {0!s}. '.format(neg_values)
          msg += 'While not forbidden, the output will look unexpected.'
          warnings.warn(msg)
docs: Raise warning for negative numbers.